If your self sponsered and do reasonably well through your training it doesn't make any difference what your A-levels were. Mine were pretty C*ap (C,D,D) reason being i found them boring so didn't work for them. My flying exams Techs/Navs however were all up in the 85%-100% mark. - Why because I actually wanted to do well in them! My present employer was really more interested in flying grades than school work. I'm not saying don't work for them good A-levels can't hurt you but it's not the end of the world if you don't get 3 A's in Maths Physics and some other related subject. A friend of mine flying for a U.K airline recently bought by BA has no A-levels , and just a hand full of GCSE's.
Good Luck with them - see you on the airways.