Hi,
The PPL Confuser is useful as a resource to aid in training for the PPL, although as has already been said is by no means a substitute for reading the manuals (Trevor Thom etc.). Again it is best to read the material and practice with the questions in the PPL Confuser and if you're getting 85% and over then you stand a good chance of passing the CAA exams (as told to me by my FTO when I did my PPL).
Also worth remembering is that the PPL Confuser is frequently updated and many copies you will buy brand new will not be a totally accurate representation of the actual CAA exams - so be careful! As a PPL and ATPL groundschool student I speak on behalf of many others when I tell you that they can be a very sneaky bunch so know your stuff and practice lots! (Chicago Convention 1944 very important to remember!).
Good Luck in the exams,
CVT Pilot.