London's Ad Consultant Guide: Vetting For Growth

I see this all the time. London founders, especially in tech and eCommerce, are burning through cash trying to find a good advertising consultant. The market is saturated with people calling themselves "growth hackers" and agencies with slick sales decks that promise the world but deliver very little. You're right to be struggling, because most people are asking the wrong questions and looking for the wrong things.

Forget the buzzwords. You don't need a "growth marketer". You need a specialist who understands paid advertising inside and out, and has a provable history of getting results for businesses like yours. The truth is, finding the right person isn't about their location in London, it's about their expertise. But since you're here, let's talk about how to cut through the noise in this city and find someone who can actually help you acheive sustainable growth.

So, why is it so hard to find someone good?

The problem usually starts with the founder. You're likely focused on the wrong criteria. You're impressed by a fancy office near Old Street, a big list of client logos (that often mean nothing), or a confident salesperson who tells you exactly what you want to hear. This is a recipe for disaster.

Most agencies and many consultants operate on a volume model. They sign you up, plug you into a standardised process, assign a junior account manager, and hope for the best. They don't have time to truly understand your business needs because their model depends on them not spending too much time on any single client. They talk about "brand awareness" and "reach" because these are easy metrics to show on a report, but they don't necessarily translate into pounds in your bank account.

Real consultants, the ones worth their fee, are different. They're obsessed with your business model, your customer lifetime value (LTV), and your profit margins. They know that getting a click is worthless if it doesn't lead to a profitable customer. They're not afraid to tell you your website is the problem, or that your offer isn't compelling enough. Their job isn't to make you feel good; it's to make you money.

Forget Promises, Demand Proof

This is the most important part. When you're vetting a consultant, their case studies are everything. But you have to know how to read them. A vague testimonial is useless. A logo on a slide is useless. You need to see the data, the strategy, and the context.

For instance, one client we worked with was a medical job matching SaaS platform. When we started, their cost per user acquisition (CPA) was around £100. That's a disaster. By restructuring their Meta and Google Ads campaigns, we brought that down to just £7. That’s a specific, meaningful result. Another one, an eCommerce subscription box client, saw a 1000% Return On Ad Spend from our Meta Ads campaigns. These are the kind of numbers that should make you sit up and pay attention. It’s not just about revenue; it’s about profitable, efficient growth.

Here’s what you should be looking for in a case study versus the usual fluff you'll get pitched:

If a potential consultant can't show you case studies with that level of detail, and for a business that is at least similar to yours (e.g. B2B SaaS, D2C eCommerce), then you should walk away. Tbh if someone asks us for references after they've seen our detailed case studies and had a free account review, it's a bit of a red flag for us as it signals a lack of trust. The proof should be right there in the work.

The Vetting Framework: A Step-by-Step Guide

Okay, so you need a process. You can't just rely on gut feeling. Finding the right consultant is too important to leave to chance. Here’s a simple framework to follow. It forces you to be systematic and to focus on what actually matters. Don't just look for a local London agency, use a proper framework for vetting paid media experts that will help you identify the right partner for your business.

What to ask on the consultation call

That third step, the "Litmus Test Call," is where you can seperate teh wheat from the chaff. Most founders let the agency lead this call and end up getting a generic sales pitch. You need to take control. This is your interview. Here are some questions you should be asking:

• -> "Based on my business, what is the single biggest opportunity you see in our paid advertising right now?" (This tests if they've done their homework).
• -> "Walk me through a campaign you ran for a client like me that failed. What went wrong and what did you learn?" (This tests for honesty and experience. Everyone has campaigns that fail).
• -> "How do you determine the initial testing budget, and how do you decide when to scale or kill an ad set?" (This tests their methodology).
• -> "What metrics will you be focusing on for my business, and why?" (The answer should be about profit, ROAS, CPA, and LTV, not impressions or clicks).
• -> "What do you need from me to be successful?" (This shows you what it will be like to work with them and tests their understanding of partnership).

A good consultant will have thoughtful, direct answers. A salesperson will give you vague, reassuring platitudes. We offer a free initial consultation where we review a potential client's strategy and ad account with them. It gives them a real taste of our expertise, and by the end of the call, they know if we're a good fit or not. Look for that same transparency and value upfront.

How much should you expect to pay in London?

This is the million-dollar question, or rather, the few-thousand-pounds question. Pricing in London is all over the place. To make an informed decision, you need to understand the models and what you're actually paying for. It's less about the absolute cost and more about the value and ROI, which is why we've put together a detailed guide on London ad agency pricing for founders.

Generally, you'll see a few common structures:

1. Monthly Retainer: A fixed fee every month. This is the most common. In London, for a decent independent consultant or small agency, you're probably looking at £2,000 - £5,000+ per month. This fee is for their time, expertise, and management. It does not include your ad spend.
2. Percentage of Ad Spend: Usually 10-20% of your monthly ad budget. This can work, but it can also incentivise the agency to just get you to spend more, not necessarily more profitably.
3. Performance-Based: A small retainer plus a percentage of the revenue generated or a bonus for hitting certain targets. This can be great for alignment, but it's rarer and usually requires a higher base spend to make the numbers work.

The real question isn't what it costs, but what it's worth. A £4,000/month consultant who helps you generate £40,000 in profitable revenue is a bargain. A £1,500/month agency that wastes your ad spend is a massive expense. You need to understand your own numbers first. What is a new customer worth to you over their lifetime (LTV)? Once you know that, you can figure out what you can afford to pay to acquire one (your Customer Acquisition Cost, or CAC).

Let's play with some numbers. Use this calculator to get a rough idea of what you can afford to pay for a new customer, which will help you judge whether a consultant's fees are reasonable for your business.

When you know you can afford to spend, say, £2,917 to acquire a customer that's worth £8,750 to you, then paying a consultant £4,000 a month to bring in several of those customers suddenly looks like a very smart investment. This is the maths that underpins all successful paid advertising. If a consultant you're talking to doesn't bring up LTV and CAC, they're not thinking about your business properly. They're just thinking about managing your ads.

The Final Word: It's a Partnership, Not a Purchase

Finding a reliable advertising consultant in London is definately a challenge, but it's far from impossible if you approach it with the right mindset. Stop thinking of it as hiring a supplier and start thinking of it as finding a strategic partner. This person or small team will be a key driver of your company's growth. They need to be someone you trust, someone who challenges you, and someone who is as obsessed with your numbers as you are.

Ultimately, a great consultant doesn't just run your ads. They help you understand your own business better. They force you to clarify your offer, understand your customers, and get ruthless about profitability. The impact goes far beyond your ad accounts. Many founders discover that properly managing their paid ad agency is the key to unlocking the next stage of growth.

If you're tired of wasting money and want to talk to a team that focuses on verifiable results, maybe we should have a chat. We offer a completely free, no-obligation strategy session where we'll look at your current advertising efforts (or lack thereof) and give you actionable advice you can implement immediately. Whether you decide to work with us or not, you'll walk away with valuable insights. If that sounds helpful, feel free to book a consultation.