MC,
There are two sets of books that are most commonly recommended for the PPL, they are the Trevor Thom series and Jeremy Pratt (AFE) series.
Opinions as to which is better are split. I think either will do the job if you put the time in. I personally chose the Pratt series, you can get them from
www.amazon.co.uk cheaper than elsewhere with free delivery. There's always PPL stuff on ebay if you don't want to pay top dollar.
The PPL confuser book is great for testing yourself, but not to learn from!
Hard to say how much time you will have to put in, or how quickly you can complete the exams, but it is possible to do an exam a week without too much stress. It all depends on how quickly you learn the material. If you have intentions to continue on and sit the ATPLs then PPL study should provide a sound foundation for them.
There are also various computer based PPL learning aids as well as audio tapes, RT CDs etc. The oxford PPL CD set is around the £300 mark, which may or may not be worth it depending on whether you prefer learning from a PC screen with graphics and animations, and if your budget extends that far.
All the best,
Simkin