Was in a similar position to you last year. I had done Maths at A level, but Physics only up to AS level.
What's been said is right - sometimes schemes appear (notably Thomas Cook and others at OAA) that require Physics, or another Science based subject. This requirement is often put in to whittle down the numbers.
Thing you need to ask yourself is, should more of these schemes crop up, you wouldn't want to be rejected on the basis of that extra qualification. No one can predict the future, but its a fairly safe bet that more of these schemes will be run, with similar requirements. Don't do yourself out of a good deal by neglecting that part of your CV. Even if it doesn't get you onto that scheme particularly, it still makes up what you might term the complete pilot CV.
Talking to some of the experienced pilots at GAPAN, they all emphasised the importance of box ticking. There might not be much between two candidates, but if you can show you've gone that little extra further in making yourself the more qualified candidate, you've got it sorted.
In the end, I did my A-Level in Physics with a distance learning provider whilst still at Uni. Awful lot of work on top of my other commitments, but its a personal choice. I'm glad I did it. PM me for details.
ETC