The best place to begin discussion of A Level resources is with an outstanding resource from OCR, an excellent teaching and learning resource, Bridging the gap between GCSE and A Level.
This is quite simply an outstanding resource for students (and their teachers!). Many exercises are provided and the answers are all at the back. OCR have very helpfully provided the document as a Word document.
The examples address misconceptions so well.
With sections on Algebra, Trigonometry and graphs including examples, question practice on key topics and suggested reading before starting the A Level this will be so valuable for students.
A complete set of worksheets to support the transition between GCSE and A Level is available from Edexcel. Choose Show more and scroll down to Transition Material.