leak detection, thermal imaging plumber suggestions

Hi,

I wondered if anyone had the name of a good plumber who has thermal imaging technology. My boiler keeps loosing pressure and our plumber said that we most likely have a leak under the floor downstairs (but we can't find any physical evidence). He said the only way he is able to check is to dig up the floors. The problem is, I have hard wood and concrete tilled floors downstairs, so taking up and replacing the floor in all the rooms downstairs would be a very expensive job.

My insurer said that they will only cover the cost of digging/repairing one hole (where the leak is located) and that I should get someone out who is able to provide thermal imaging to locate the suspected leak. Has anyone had this problem before and know a good company/plumber/engineer who can locate the leak through thermal imaging? -I'm based in the London Borough of Harrow

Thank you in advance