I am using the OAT cbt Cd's (I found them £50 cheaper on a web site that's named after a rain forest!!) and although very in depth i find it an easier way to learn than going through books, i think CATS also do a cbt course for the PPL.
It all comes down to whats best for you and the way you learn. If you aren't planning to go onto ATPL then maybe give the OAT'S a miss as they teach you more than you really need to know for just the PPL.
One thing you definitely need is the confuser if you haven't purchased that already.
Either way best of luck
