Yes - if you are in London there are only half a dozen or so airfields and not that many more training organisations to check out, so go and have a look. A nice day out - a trip to an airfield taking in the atmosphere. Lunch or just a coffee, a chat with the trainers, and on to the next. Fun in itself, and the best way to find out. As a prospective client, people will be very nice to you.
Just don't agree to pay for a block of flying up front - bad things have happened in the past when clubs have gone bust, and now is sadly a bad time for any business.
B