If you want me to be terribly honest, seeing as you're only year 9 and you have two whole years until the GCSEs, I wouldn't care about preparing now. The GCSEs are extremely easy and two years advance preparation is not imperative to achieve A*s. I studied for only 1 and a half months in advance and attained 6 A*s. Right now, this is your time to relax, before you feel the kick of the A levels :P