Simon W: Yep, I am at BAFC. I did not bother with the ground school and just used the Trevor Thom books, and, more importantly, the indispensable PPL Confuser Book (they sell it at the club I think.
Using the practice questions in the Confuser, you can ascertain when/whether you're ready to sit one of the tests. My approach is always to read the relevant book, then do the Confuser questions until I get them all right, then sit the paper.
Hope this helps,
Andy