The confuser is out of print. I have the AFE Question and answer simplifier (5th Edition) which is excellent.
I got it new from the AFE/Airplan web site. It has mock exams, reasoning for the answers and revision notes. Brilliant book.
Most people do the exams with their school, that's what I'm doing. I was told there was a chap a Cranfield who would just do ground school revision and then the exams, and there is a chap who always advertises in Pilot and Flyer.