I agree with all other posts on this thread. The idea is that if you enjoy Physics at "A" level you will therefore understand it. If you understand the principles that it teaches then many topics in the aviation courses that follow will be that much easier to understand and you will stand a better chance of passing them. With regard to your medical, then a class 1 is essential, so see the CAA soonest. What is more important that getting a class 1 now is for how long you can reasonably expect to keep it. Remember those b****s can take it away in an instant without warning and you are left with no job, no income and no prospects. In your case the backstop of an additional qualification to help on the employment stakes should the unthinkable happen is thus even more worthy of serious consideration.
best of luck