Well here is a vote for Cabair at Elstree. I did my IMC with them a few years back. Now I admit they are not the cheapest on the block. For schools near to London, that honour has to go to a small school in West London.
But the quality of instruction was excellent. I never had a plane or instructor availability issue, the quality of the course as a whole was very good, materials good etc. A professionally run course.
And in reality I would rather pay more and have to travel less for my lessons - if to save £5 on the landing fee and £10 per hour on the hire, I have to drive an extra 30 minutes each way, well, that's an easy decision, I'd pay the extra and save the mileage on my car, the petrol in my tank and my weekend time. Not everyone's view I am sure. But there then convenience is very high on my own wish list.
As someone else said, usually you get what you pay for.