RTN11's spot on with the comments on Bristol's question bank.
I found that the HPL, Air Law and Radio Nav exams were virtually indistinguishable from the Question Bank.
My POF exam (April 08) had at least 40% of the questions which I didn't recognise from the question banks. Likewise, I personally feel that POF, Performance, M+B, Radio Nav, Met and Air Law are bread and butter subjects for ATPL candidates so the objective should be to learn it to the best of your ability.
The question banks (as there are several now)
On the good side, there were very few stability questions in my POF exam, and those that were there were fairly easy. It's not a subject I can speak confidently about and stick force stability is still a bit of a mystery.
Regards,
Obs