London has more web design agencies than you can shake a USB stick at. They range from one-person operations working from a Hackney flat to 200-person digital agencies with offices in Shoreditch and New York. They all have polished websites, confident sales pitches, and glowing testimonials.
So how do you actually tell the difference between an agency that will transform your online presence and one that takes your money, delivers a template dressed up as custom work, and disappears after launch?
This guide is the honest answer to that question.
The Red Flags Nobody Warns You About
Let's start with what to run from, because that's more useful than generic advice about "checking portfolios."
No case studies with actual results. Pretty portfolio screenshots are meaningless. Any decent designer can make something look nice. What you want to see is this: client had a problem, agency did this specific work, here's what changed — traffic, leads, revenue. If an agency's portfolio is all aesthetics and no outcomes, they're design-first, not results-first.
Vague or wildly inconsistent pricing. "It depends" is a legitimate answer to some questions. If you ask for a rough budget range for a ten-page service website and an agency refuses to even give you a ballpark, that's a problem. Either they haven't built enough similar projects to know, or they're fishing to understand your budget before quoting to it. Neither is good.
Guaranteed top Google rankings. Any agency that promises you "number one on Google" as part of their web build is lying. Rankings depend on dozens of factors, many of which take months to influence. No responsible agency promises specific ranking positions. They'll talk about strategy, structure, and process — not guaranteed outcomes.
Disappearing after launch. Ask explicitly: what's your post-launch support model? Some agencies hand over the files and vanish. That's fine if you have internal technical resources, but for most businesses it's a disaster. A site with no ongoing support is a liability — plugins stop being maintained, hosting expires, things break.
No questions about your business. If an agency's first call is mostly them telling you about themselves and barely asks about your customers, your competitors, or what success looks like for you — that's telling. A results-focused agency needs to understand your business before they can design anything useful.
Green Flags: What Good Looks Like
A clear, documented process. Good agencies can walk you through exactly what happens from briefing to launch. Discovery, wireframes, design, build, testing, launch, handover — each stage with defined outputs and client checkpoints. If the process is vague or the agency "just gets on with it," that's not confidence, it's chaos.
SEO-aware from the start. Web design and SEO are not separate things. The structure of your site, the page URLs, the heading hierarchy, the internal linking, the content — all of it affects how Google sees and ranks your site. An agency that treats SEO as something you bolt on after launch doesn't understand how the web actually works. Ask them specifically how they approach SEO during a build. Listen carefully.
Transparent pricing. You should know roughly what's included, what's not, and what would cause the price to change before you sign anything. Scope creep happens, but good agencies manage it with change requests and clear communication — not surprise invoices.
Post-launch support with defined terms. Ask what happens in the first 30 days after launch (the period when bugs most commonly appear). Ask what happens in month four when your plugin needs an update. A retainer, a support package, or at least a clear process for how to raise issues.
They push back on your brief. This sounds counterintuitive, but the best agencies challenge your assumptions. If you say "I want a big homepage slider" and they agree without question, they're people-pleasing, not advising. A good agency will say "sliders tend to hurt load speed and conversion rates — here's what we'd suggest instead." You want expertise, not compliance.
The Questions That Actually Matter
Most businesses go into agency meetings and ask variations of "how long does it take" and "can I see some examples." Those are fine questions but they won't tell you who to hire. These will:
"Can you show me a site you built and tell me what changed for that client after launch?" This forces them to connect design to outcomes. If they can't answer this for at least two or three clients, be cautious.
"How do you handle SEO during a build, specifically?" Not "do you do SEO" — everyone says yes to that. Ask specifically. What do they do with page structure? How do they approach keyword-informed content architecture? Do they check Core Web Vitals before launch?
"What platform will you build on and why?" The answer should be specific and justified. WordPress for most content-led sites is completely reasonable. A custom React build might be right for a complex application. What's not acceptable is "we build on [Platform X] because that's what we know" without any consideration of whether it's right for you.
"Who will actually be working on my project?" At larger agencies, you might be sold by a senior partner and then handed to a junior developer you've never met. Know who your day-to-day contact is, who's doing the design, and who's writing the code.
"What happens if I'm not happy with the design direction?" Every agency has a process for revisions. Understanding it upfront prevents painful conversations later. How many revision rounds are included? What happens after that?
For a more comprehensive list, we've put together a full set of questions to ask a web design agency — cover those before you sign anything.
Design-First vs Results-First: A Real Distinction
This is the most important distinction in the market, and agencies rarely make it explicit.
Design-first agencies care deeply about aesthetics, typography, visual identity. They build beautiful websites. They win design awards. Their portfolio looks spectacular. The problem is that beautiful doesn't always convert, and a stunning site with no traffic and no leads is a very expensive way to feel good about your online presence.
Results-first agencies start with the commercial question: what do we want people to do when they land on this site, and how do we make that as easy as possible? Design serves that goal — it's not the goal itself. They're thinking about conversion rates, SEO performance, page speed, lead capture, and measurable outcomes.
The best agencies are both. They build things that look great and perform commercially. But if you have to choose — and in practice you often do — a results-first approach is more valuable for most businesses.
Retainer vs Project: What Makes More Sense
Most agencies offer either project-based work (fixed scope, fixed price, defined deliverables) or retainer arrangements (ongoing monthly work, often combining maintenance, SEO, content, and design updates).
Project-based works well when you know exactly what you need, have clear specifications, and have internal resources to manage the site after launch. You pay, you get a website, the engagement ends.
Retainers work better when you want ongoing performance improvement — rankings climbing, conversion rates improving, content growing. The agency becomes a long-term partner invested in your continued growth, not just in delivering a project.
For most ambitious SMEs, a project to build the site followed by a retainer for SEO and ongoing development is the sweet spot. The build gives you the foundation. The retainer compounds the value over time.
Our web design and development services are structured to offer both — a proper build followed by the option to continue working together as your business grows.
Budget Realism for London
London agencies are more expensive than provincial equivalents. There's a premium for location, overhead, and often for working with bigger clients. That premium can be worth it — London agencies generally have seen more variety, worked on more complex projects, and have sharper commercial instincts.
Expect to pay 20–40% more for a London-based agency compared to equivalent work outside the capital. A well-built ten-page service website from a solid London agency runs £5,000–£12,000. Full custom builds with ecommerce, CRM integration, or complex functionality will be £15,000–£40,000+.
If someone in London is quoting you £1,500 for a bespoke website, something is wrong. They're either using a £50 template, outsourcing offshore, or undercharging because they're new and want portfolio work. That can be fine if you understand what you're getting — but it's not "custom web design."
One More Thing
The agency you choose is choosing a business partner, not just buying a service. You'll be working with these people closely for several months during the build, and potentially for years if you do a retainer. Their values matter. Their communication style matters. Their responsiveness to questions matters.
Before you sign, ask for a reference from a current client. Not one they've specifically prepped — just a client you can call and ask honestly: was this agency good to work with? Did they deliver what they promised? Would you use them again?
The answer will tell you everything you need to know.
If you want to understand more about what a genuinely custom build involves vs what you get from template work, our post on what bespoke web design actually means is a useful next read.
And if you'd like to talk about what your specific project needs, our web design team is happy to have a straightforward conversation — no hard sell, just honest advice about what would work for your situation.