I teach a lot of groundschool at PPL level and have found the JAR PPL Perfector to be the most relevant for the exams. However there are a few annoying errors dotted here and there, with the wrong answers given. Hopefully this will be rectified in the 2nd edition.
Overall though, a good buy and for my students it has definitely been useful - alongside some decent groundschool instruction of course
The PPL Confuser is a bit out of date now and for example only offers 3 alternative answers to each question when the exam papers have 4 to choose from.
The Simplifier is not so well matched to the way that the questions and answers are written in the real papers. However it is a good way of checking knowledge.