I think the A-levels in Physics, Maths would be beneficial but not essential. I think the fact that the RAF ask for 2 A levels at E or above proves that as long as you have the right aptitude and attitude you can make it through.
I have E grades in Geology, Geography and Biology, but I still got into the RAF as a Navigator and now fly 757's commercially. So I think the best choices you can make are the ones you actually enjoy as apposed as what you "think" you should do.