PPSC CD-ROM won't help you. It's overburdened with stuff you don't need to know. I found climatology a bit of a 'mare until I did the 2 week cse at BGS and by the time they've gone through the material and you've done all the papers you'll be be more than happy. Their met revision papers are, incidentally, excellent and don't just give the answer but a whole worked solution and rationale behind the answer which is a huge aid to understanding.
Trick to climatology is understanding the principles really thoroughly and then applying them. Don't try and memorize everything but apply some commonsense and the basic rules that you are taught. Good luck.