I happen to know you could knock at least £1000 off the figures quoted in 'fostex' estimation, if not more.
Here is their website and prices. PPL instruction is charged at £20/hour, and their C150 is £100/hour. Ground exams are £20, and there are no landing fees at Breighton. The only membership required is £55/year payable to The Real Aeroplane Club in order to fly from Breighton, but this gives free reciprocal landing fees to many local (and a bit further away) airfields.
YOU WOULD HAVE TO BE A COMPLETE NUMPTY to not consider this outfit. Feel free to turn up on a weekend for a chat and look around.