Over the past six years running MattDarm, I've audited hundreds of UK business websites. One pattern I've noticed consistently: most are leaving performance on the table. Not just a little bit — we're talking 15–25 points on Google PageSpeed Insights that could be reclaimed with the right strategy.
The irony? Many business owners know their site is slow. They've felt it. But they don't know where to start fixing it, so nothing gets done. And meanwhile, their competitors who invested in speed are outranking them in Google search results and converting more visitors.
I've personally guided clients from PageSpeed scores in the 30s and 40s to the 90+ range. And I want to share exactly how I do it — because speed isn't just a technical nice-to-have anymore. It's a ranking factor. It's a conversion lever. And it's absolutely achievable.
In this guide, I'm covering both the WordPress optimisations that move the needle and the next-gen approach — Next.js — that eliminates most performance bottlenecks entirely. By the end, you'll know which path is right for your business.
Why PageSpeed Matters More Than Ever
Let me start with the facts.
Google has been explicit since 2021: site speed is a ranking factor. But the business impact goes far deeper than SEO. According to research from Deloitte, a one-second delay in page load time can drop conversion rates by 7%. For an ecommerce site turning over £500k per year, that's potentially £35,000 in lost revenue annually from speed alone.
And it's not just about money. User experience is the real metric. When a user lands on your site and it takes four or five seconds to load, they leave. They go to a competitor. The bounce rate climbs, session duration plummets, and engagement dies.
Google knows this. That's why they built PageSpeed Insights and the underlying Core Web Vitals metrics. They're not arbitrary measurements — they're directly correlated with user satisfaction.
For UK businesses specifically, this matters more than most realise. Our market is competitive. Customers expect fast, responsive websites. They've been trained by Amazon, by Google, by Stripe. A slow site reads as unprofessional or outdated. A fast site reads as trustworthy and modern.
Understanding the Metrics: What PageSpeed Insights Actually Measures
Before we optimise, we need to understand what we're measuring. Google PageSpeed Insights pulls from several key metrics:
Core Web Vitals are the headline metrics. These are what Google cares most about:
Largest Contentful Paint (LCP) measures how long until the largest visible element on the page (usually an image or heading) is rendered. Google wants this under 2.5 seconds.
Cumulative Layout Shift (CLS) measures how much the page layout shifts around as it loads. Anything under 0.1 is good; over 0.25 is poor. If a user is about to click a button and it suddenly moves, that's high CLS.
Interaction to Next Paint (INP) measures the latency of all user interactions. Google wants this under 200 milliseconds. This replaced First Input Delay in 2024 and is now the standard responsiveness metric.
Then there are supporting metrics: First Contentful Paint (FCP) should be under 1.8 seconds, Speed Index measures how quickly the page visually completes, and Time to Interactive (TTI) tells you when the user can actually interact with the page.
The reason I'm spelling these out is simple: if you don't measure these individually, you're flying blind. PageSpeed Insights gives you a single score out of 100, but that score is a weighted average. You could have brilliant LCP and dreadful CLS, and the overall score masks the real problem.
My approach is to look at each metric, identify which ones are dragging your score down, and target those specifically.
The WordPress Reality: How Most UK Businesses Are Currently Built
Let's be honest: if you're running a website in the UK right now, there's roughly a 50% chance it's on WordPress. WordPress dominates small-to-medium business web development, and for good reason — it's flexible, accessible, and there's a massive ecosystem of plugins.
But WordPress comes with an inherent performance tax.
A typical WordPress setup looks like this: shared or lower-tier hosting (because it's cheap), 8-12 plugins running on every page load (page builder, SEO plugin, caching, security, backup, forms, analytics), a bloated feature-rich theme with lots of CSS and JavaScript bundled in, and unoptimised database queries stacking up from each plugin.
The result? Average mobile page load time on WordPress is 4.8 seconds. On a 4G connection in a rural part of the UK, it can be much worse.
I've measured this across dozens of client sites. A typical WordPress business website scores 35–55 on PageSpeed Insights mobile. Some score in the 20s.
But here's the thing: WordPress can be optimised. It's not a lost cause. I've helped clients push WordPress sites from 40 to 75–80 on PageSpeed Insights. It just requires discipline and the right approach.
WordPress Optimisation: The Priority Order
1. Hosting Matters — More Than You'd Think
Shared hosting is cheap for a reason. You're sharing server resources with dozens or hundreds of other websites. When one of them gets traffic, your site gets slower.
Move to a dedicated or managed WordPress host. Services like Kinsta, WP Engine, or Pressable are more expensive (£20–50+ per month), but their servers are optimised for WordPress with Redis caching, fast SSDs, and optimised PHP configurations.
I've seen sites jump 10–15 points on PageSpeed Insights just from moving to better hosting. It's the cheapest bang-for-buck optimisation available.
2. Upgrade PHP to 8.1 or 8.2
This is free and quick. Most hosts have a simple control panel toggle. PHP 8.1 is roughly 2x faster than PHP 7.4 for executing WordPress code. There's no reason not to do this immediately.
3. Implement Proper Caching
WordPress generates HTML on every page load by default. That's wasteful. Implement page caching so the HTML is generated once and served as static files.
Use a caching plugin like WP Super Cache (free) or WP Rocket (paid, £39/year). These cache pages to disk or in memory, and serve cached versions to repeat visitors. This alone can cut page load time by 30–50%.
4. Optimise Images Aggressively
Images account for the majority of page weight on most websites. Resize images to the exact dimensions needed (don't upload a 4000px image and scale it down in HTML). Convert to WebP format — WebP is 25–35% smaller than JPEG at the same visual quality. Use an image optimisation plugin like Smush or ShortPixel to compress and convert automatically. And lazy-load images below the fold so they don't block initial page load.
5. Remove Unused Plugins and Theme Features
Every plugin and theme file slows down page load. Audit your plugins and delete anything you're not actively using. I've removed 4–5 plugins from WordPress sites and seen 5–10 point jumps in PageSpeed score.
6. Defer Non-Critical JavaScript
WordPress loads all JavaScript in the head by default. This blocks rendering. Use a plugin to defer non-critical JavaScript (analytics, third-party widgets, etc.) or load it asynchronously. This is particularly important for Google Ads tracking scripts which often add significant weight.
7. Minify CSS and JavaScript
Every file should be minified (whitespace removed, variable names shortened). Use WP Rocket or Autoptimize to handle this automatically.
How High Can WordPress Actually Go?
With disciplined optimisation, I've gotten WordPress sites to 75–85 on mobile PageSpeed Insights. Sometimes higher if the site is relatively simple.
But there's a ceiling. It's very hard to break 85 on mobile with WordPress, and nearly impossible to consistently hit 90+. Why? Because of architectural constraints: server-side PHP processing overhead on every request, plugin bloat that can't be fully eliminated, database queries (20–50 per page load), and no automatic code splitting.
So if your goal is 90+ on PageSpeed Insights, you have a choice: accept 80–85 as your ceiling, or consider a different approach.
The Next.js Advantage: Breaking Through the Ceiling
Here's the comparison that changes most conversations I have with clients:
WordPress averages 4.8 seconds mobile page load, scoring 50–75 on mobile PageSpeed. Next.js averages 0.9 seconds mobile page load, scoring 92–98 on mobile PageSpeed. That's a 5x difference in page load time. And it's not because of optimisation magic — it's because the architecture is fundamentally different.
Why Next.js Is Fast by Default
Static Generation (SSG) — Next.js can generate pages as static HTML files at build time. When a user requests your page, they're not waiting for a server to render anything — they're downloading a pre-built HTML file from a global CDN. This is faster than anything WordPress can do. For a brochure site, blog, or product page, this is perfect.
Server-Side Rendering (SSR) Without the Overhead — For pages that need dynamic content, Next.js renders on the server efficiently. Compare this to WordPress, where every page request hits the database and runs PHP processing for every single visitor.
Built-In Image Optimisation — Next.js includes an Image component that automatically resizes images for different screen sizes, converts to modern formats (WebP, AVIF), lazy-loads images below the fold, and serves images from a global CDN. No plugin needed.
Code Splitting by Default — Next.js automatically splits JavaScript by page. Your homepage doesn't load the JavaScript for your contact form. Your blog post doesn't load the JavaScript for your product filters. This keeps file sizes minimal.
Global CDN Distribution — When deployed to Vercel, your site is served from servers around the world. A user in Edinburgh hits a UK server. A user in Australia hits an Australian server. Latency drops dramatically.
At MattDarm, we build all our sites with Next.js, and they consistently score 95+ on PageSpeed Insights mobile. Every page. That's the difference a proper tech stack makes when you invest in custom website design.
When to Choose WordPress vs Next.js
To be fair, WordPress has its place. Choose WordPress if you need a system that's easy to update without a developer, your budget is tight, and you don't mind a PageSpeed score in the 70–80 range.
Choose Next.js if you want 90+ PageSpeed scores, you care deeply about user experience and SEO performance, you want fast reliable hosting without constant maintenance, and you're willing to invest in a proper build.
For a professional service business or ecommerce store, I almost always recommend Next.js. The performance advantage translates directly to better rankings and higher conversion rates.
Quick Wins: What You Can Do Today
If you're not ready to rebuild your site, here are seven high-impact optimisations you can implement this week:
Enable Caching (1 hour) — Install WP Super Cache or WP Rocket. Enable page caching. This often yields a 10–15 point jump immediately.
Compress Images (2 hours) — Go through your top 10 pages and compress images using TinyPNG or ShortPixel. Convert to WebP. This can save 1–2 seconds of load time per page.
Upgrade PHP (30 minutes) — Ask your host to upgrade you to PHP 8.2. Verify it doesn't break anything.
Remove Unused Plugins (1 hour) — Audit your plugins. Delete anything you're not actively using.
Lazy-Load Offscreen Images (30 minutes) — Use the native loading="lazy" attribute on images, or let a plugin handle it.
Defer Non-Critical JavaScript (1 hour) — Use WP Rocket's "Delay JavaScript Execution" feature or Autoptimize's "Defer JS" option.
Upgrade Hosting (Ongoing) — If you're on shared hosting, move to Kinsta or WP Engine. Your PageSpeed score will jump 15–20 points.
Implement these seven changes and you'll likely move from 50 to 70+ on PageSpeed Insights mobile. Not 90+, but a significant improvement.
Monitoring and Measuring Progress
You can't improve what you don't measure. Here's what I recommend:
Use PageSpeed Insights — Visit pagespeed.web.dev, enter your domain, and get a detailed report. Test both mobile and desktop. Mobile is more important for ranking.
Check Core Web Vitals in Google Search Console — Go to Core Web Vitals and see your real-world performance from actual user sessions. This is "field" data versus PageSpeed Insights' "lab" data, and they can differ significantly.
Use Lighthouse in Chrome DevTools — Right-click any page, select "Inspect," go to the Lighthouse tab, and run a report. This is the same engine that powers PageSpeed Insights, just in your browser.
Monitor Over Time — Set a baseline today. Implement optimisations weekly. Check PageSpeed Insights monthly. You should see steady improvement.
The Business Case: Speed Equals Revenue
Let me make the financial case clearly.
A one-second improvement in page load time increases conversions by 7% on average. For a business generating £20,000/month from their website, that's £1,400 per month — £16,800 per year — from speed improvement alone.
Google also gives faster sites a ranking boost. If you move from page 2 to page 1 of Google results, you'll see a 10-30x increase in organic traffic. Speed alone won't get you there, but combined with solid SEO and great content, it's a significant factor.
And consider the user experience angle: 53% of mobile users abandon sites that take longer than 3 seconds to load. If your WordPress site loads in 4.8 seconds, you're losing over half your mobile visitors before they see a single word of your content.
The investment in performance — whether that's WordPress optimisation or a Next.js rebuild — pays for itself through improved search rankings, higher conversion rates, and lower bounce rates.
Frequently Asked Questions
Does PageSpeed Insights score directly affect Google rankings?
Core Web Vitals (which PageSpeed measures) are a confirmed Google ranking factor. However, they're one of hundreds of signals. A site with poor PageSpeed but excellent content might still rank. But all else being equal, a faster site ranks higher. For competitive UK markets, every advantage counts.
Can I hit 90+ on PageSpeed with WordPress?
It's extremely difficult for a typical business WordPress site. With aggressive optimisation, excellent hosting, and minimal plugins, you might reach 85-88 on mobile. Simple brochure sites with no page builders can occasionally hit 90. But for a feature-rich WordPress site, 75-85 is the realistic ceiling.
What's the difference between PageSpeed Insights and GTmetrix?
PageSpeed Insights uses Google's Lighthouse engine — the official metric Google uses for ranking. GTmetrix uses Lighthouse plus additional metrics. For search ranking purposes, PageSpeed Insights is the source of truth. Use both: PageSpeed Insights for the Google score, GTmetrix for deeper analysis.
Is Next.js harder to maintain than WordPress?
In some ways, yes — you can't log into an admin panel and drag-and-drop changes. But in other ways, Next.js is easier to maintain: no plugin updates, no security patches, no database optimisation. Content updates can be managed through a headless CMS like Sanity. The tradeoff is developer dependency versus ongoing maintenance burden.
Should I prioritise mobile or desktop PageSpeed?
Mobile. Google primarily ranks based on mobile experience, and over 60% of UK web traffic is mobile. A mobile score of 85 is more valuable than a desktop score of 95. That said, don't neglect desktop — aim for 85+ on both.
Ready to Improve Your Site's Performance?
PageSpeed Insights isn't a vanity metric. It's a direct measure of user experience and a ranking factor Google explicitly uses.
If your site is scoring below 75 on mobile, you're leaving money on the table. Every day with a slow site means lower rankings, higher bounce rates, and fewer conversions.
The good news: you can fix this. Whether you're optimising WordPress or rebuilding on Next.js, the path is clear.
If you want expert help, we offer two approaches at MattDarm. We can optimise your existing WordPress site to push it as high as the platform allows. Or we can build you a custom Next.js site that scores 95+ from day one.
Either way, the investment pays for itself through improved rankings and higher conversion rates. Get in touch to discuss your site's performance.
In the meantime, run your site through PageSpeed Insights and check your real-world performance in Google Search Console. That baseline is your starting point.
If you're also looking to improve your search visibility beyond speed, check out our SEO services and our guide to getting cited by AI search engines.
