London's Guide To Vetting Google Ads Agencies

Finding a decent Google Ads agency in London feels like a nightmare, doesn't it? You're drowning in a sea of agencies all promising the world, all with flashy offices in Shoreditch or Canary Wharf, and all using the same buzzwords. The truth is, most of them are average at best. They're generalists who can run a basic campaign, but they lack the sharp, specific expertise to actually move the needle for a business like yours. They spend more time on their sales deck than on their clients' accounts.

You're right to be sceptical. Your business needs measurable results, not a monthly report full of fluffy metrics. The good news is there are some genuinely brilliant specialists out there, but you have to know how to spot them. It's not about the size of their team or the swankiness of their office; it's about a track record of raw, provable performance. This guide will give you a no-nonsense framework to cut through the rubbish and find a partner that will actually make you money. If you get this right, you can avoid months of wasted budget and frustration, which is why we've also written a guide on how to stop wasting money on Google Ads in a market like London.

So, what am I actually looking for then?

Right, let's get one thing straight. You are not looking for a "full-service digital marketing agency". That's code for "master of none". They'll offer you SEO, social media management, email marketing, and PPC, but they won't be truly exceptional at any of it. You need a specialist. A team that lives and breathes Google Ads, day in, day out.

Here’s what really matters:

-> Niche Expertise: Have they worked with businesses like yours before? If you're a B2B SaaS company, an agency that primarily works with local e-commerce stores is not going to understand your sales cycle, your customer lifetime value, or the mindset of your target audience. I've run countless campaigns for software companies, and the strategy is completely different. One of our clients, a medical job matching SaaS, was paying £100 per user acquisition before we came in. By applying a specialist B2B strategy, we got that down to £7. A generalist agency would never have known how to do that.

-> Provable Results (in £): This is non-negotiable. Don't let them talk about "brand awareness" or "click-through rates". Those are secondary metrics. You need to see case studies with hard numbers. How much revenue did they generate? What was the Return On Ad Spend (ROAS)? What was the cost per lead or sale? They should be able to show you, for example, how we generated £107k in revenue for a client at 618% ROAS. If their case studies are vague and full of percentages without actual figures, it’s a huge red flag.

-> Honesty and Transparency: A good agency will be brutally honest with you. They won't promise you the #1 spot on Google overnight. Tbh, in paid advertising, you can't really promise anything as it's impossible to predict how ads will perform. They'll tell you what's realistic, what the challenges are, and what kind of budget is genuinely needed to compete in the London market. They should also give you full, admin-level access to your own Google Ads account. If they want to run it through their own master account where you can't see everything, run for the hills. It's your data, your money.

Finding an agency that ticks these boxes requires a proper system. We've actually built a proper framework for vetting paid ads agencies that you can follow step-by-step.

How do I know if their case studies are legit?

This is where you need to put your detective hat on. A slick PDF with a logo on it means nothing. You need to tear it apart and see if it holds up to scrutiny. A lot of agencies will show you vanity metrics to distract you from the fact they didn't actually make their client any money.

Here's a simple process to follow when you're reviewing a case study:

For example, if an agency tells you they got "10 million views for a luxury brand," that sounds impressive. But what did it achieve? Did it lead to sales? If you're a B2B founder, you probably care more about an agency that generated leads from decision makers at a $22 CPL. That's a real business outcome. If you are a founder looking for help with your B2B ads, have a look at our guide on what to do if you need B2B leads from Google Ads. The context is everything. Don't be afraid to ask probing questions about the case studies they present. A good agency will welcome it.

What killer questions should I ask on the first call?

The discovery call is your interview. They are trying to win your business, but you are trying to see if they're actually competent. Don't let them run through their standard sales pitch. Take control and ask questions that force them to demonstrate their expertise on the spot.

Here are a few of my favourites:

1. "Based on what you've seen of our website and business, what do you think our biggest immediate opportunity with Google Ads is?"
This question instantly seperates the experts from the salespeople. A salesperson will give a vague answer like "we need to optimise your keywords and improve your quality score." An expert will say something specific: "I see you're not running any Performance Max campaigns for your top-selling products, and your shopping feed is missing key attributes. We could likely see a 20% uplift in ROAS within the first month just by fixing that." They'll provide a mini-audit on the spot.

2. "Can you walk me through a campaign you're currently running for a client similar to us? What's working and what isn't?"
This forces them to go beyond the polished case study. It shows you how they think in real-time about real-world campaigns. They should be able to talk about specific ad groups, keywords they're testing, landing page A/B tests they're running, and the actual results they're seeing this week, not six months ago.

3. "What don't you do? What kind of client is a bad fit for you?"
This is a test of honesty and focus. A great agency knows its strengths and weaknesses. They might say, "We don't do organic social media," or "We're not a good fit for clients with a budget under £2,000/month because we can't get enough data to optimise effectively." An agency that claims to do everything for everyone is a major red flag.

4. "How will you measure success and what will my first month's report look like?"
You want to hear them talk about business metrics. Their answer should be focused on leads, sales, revenue, and ROAS. Ask to see a sample report. Is it a clear, concise summary of performance against your goals, or is it a 20-page document filled with confusing charts and jargon designed to overwhelm you? Clarity and a focus on what matters are what you're looking for. These questions are part of our complete vetting framework for B2B agencies, but they apply to almost any business.

Okay, but what's this actually going to cost me in London?

This is the big question, and the answer is... it varies. But you can forget finding anyone credible for a few hundred quid a month. The London market is expensive, and real expertise comes at a price. Anyone charging rock-bottom fees is likely inexperienced, overloaded with clients, or outsourcing the work to someone cheap. You get what you pay for.

Here are the common pricing models:

• Flat Monthly Retainer: This is the most common. You pay a fixed fee each month for the managment of your account. It's predictable and easy to budget for.
• Percentage of Ad Spend: Common for larger accounts. The agency takes a cut of your monthly spend, typically 10-20%. This can incentivise them to get you to spend more, not necessarily more efficiently.
• Performance-Based: Less common, but some agencies offer it. They might charge a lower retainer plus a bonus for hitting certain targets (e.g., a percentage of revenue generated). This can align incentives well, but the terms need to be crystal clear.

In London, for a good specialist agency, you should expect to pay a monthly retainer that reflects your ad spend. Here's a rough guide:

This might seem like a lot, but you have to stop thinking about it as a cost. It's an investment. The real question isn't "how much does it cost?", but "what is a new customer worth to my business?". If you don't know this number, you can't possibly judge if your ad spend is profitable. You need to calculate your Customer Lifetime Value (LTV).

Once you know you can afford to spend, say, £3,333 to acquire a customer worth £10,000, paying a £3,000/month agency retainer to bring in two of those customers a month doesn't seem expensive at all. It seems like a bargain. This is the maths that unlocks aggressive growth. For a more complete overview, have a look at our detailed breakdown of London PPC costs.

What are the big red flags to watch out for?

Your goal during the vetting process is not just to find the good signs, but also to spot the bad ones. Here are the things that should make you immediately suspicious.

• The "Guarantee": Anyone who "guarantees" results like a #1 ranking or a specific number of leads is either lying or misunderstanding how Google Ads works. The auction is a dynamic, competitive environment. There are no guarantees. This is the biggest red flag in the industry.
• Long-Term Lock-in Contracts: A confident agency doesn't need to lock you into a 12-month contract from day one. They should be able to prove their value within 3-6 months. A 3-month initial term followed by a 30-day rolling contract is fair. It keeps them accountable.
• Lack of Access: If they insist on running campaigns through their own account and only provide you with PDF reports, it's a no-go. You should have full, 24/7 admin access to your own Google Ads account. It's your asset.
• One-Size-Fits-All Strategy: If their proposal looks generic and doesn't mention your specific business goals, competitors, or target audience, they haven't done their homework. They're just trying to fit you into their pre-made box.
• The Account Manager Shuffle: Ask who, specifically, will be working on your account. Often, you'll be sold by a senior strategist, then handed off to a junior account manager with little experience. You need to know the level of expertise being applied day-to-day.

You may also be wondering about the difference between hiring a freelancer versus an agency. The best approach often comes down to budget and complexity, and it's worth understanding the pros and cons before deciding whether you need a freelancer or a full agency. A freelancer can be great for smaller budgets, but an agency often brings a wider range of skills and resources for more complex accounts.

My final advice for you

Choosing an agency is a big decision, and it's easy to get it wrong in a saturated market like London. To make it simpler, I've boiled down my entire vetting process into a final checklist.

This is the main advice I have for you:

Ultimately, trust your gut. You're not just hiring a supplier; you're bringing on a growth partner. The right agency should feel like an extension of your own team, obsessed with the same numbers you are. By following this framework, you'll be able to confidently seperate the talkers from the doers and find an agency that can truly deliver the measurable results your business needs to grow.

It's a lot to take in, and even with the right framework, doing this kind of in-depth vetting takes time and expertise. Sometimes it's easier to talk it through with someone who's been on both sides of the table. If you'd like an expert opinion on your current situation or help figuring out what your next steps should be, consider scheduling a free, no-obligation consultation. We can take a look at your business and give you some honest advice on the best path forward.

Hope this helps!