Key Stage 5
KS5 Useful Revision Sites
http://www.examsolutions.net/a-level-maths-papers/index.php - This is a brilliant free site with a video solution for each question alongside a copy of the paper to download and try first.
http://www.mathsnetalevel.com/index.php - this site costs only costs £12 to sign up for year 12 (or £24 for access to 12 and 13 material). Highly recommended for struggling students