I'd recomend buying the books (Thom etc) and then buy the PPL confuser. It's a lot cheaper and in the long run probably a better way to learn. (IMHO)
I used Mr Davidson, for a couple of exams. His organisation is very good, but when you add up the cost of acomodation etc you'd be better spending the money on flying.
Does your flying school not offer ground school through the winter months?
I see you're from Stevenage, I'd highly recomend the RT course run by Henlow flying club. You don't have to be a member and it's run over a number of evenings by an ATC from Luton, Very nice guy and good fun, also he'll give you the test at the end of the course, plus lots of 'real world' advice on RT.
CC