I don't know about sites to download but I would reccomend buying the "PPL Confuser" £20. This has ALL the questions in ALL subjects & all answers. There are I believe 3 different papers per subject, you won't know which one you will get till the examiner gives it to you. For instance, the Confuser has 191 questions & 4 choice answers each on Air Law, of which 40 will be on the exam paper, Well worth the money & the batteries don't run out!
Good luck.