Just throwing this out there: you might want to make sure that wherever you're planning to go to for sixth form runs their maths course with the same board (presuming you want to take maths A level) otherwise you may end up having to do the AS again anyway. I did C1 a year early as well but it was more of a sideline as we had half the amount of lessons and didn't do any homework for it. To be honest, we'd have been better off doing statistics GCSE or additional maths GCSE. sorry if i strayed slightly off topic....