In all honesty, none
I haven't got any A levels, I bailed out of school at 16 with a handful of O levels, did a BTEC course and went to work. After 8 years I re-trained to become a pilot, I hadn't touched the controls of any type of aeroplane before then. I was pretty useless at maths, but I did manage an O level pass somehow, but I still struggle now with even basic maths, so that dispels that one as it doesn't appear to have held me up any, although it did make Perf E and loading very difficult for me, failed both of those first time round!
I reckon what counts most is whether you really want it, if you do then you knuckle down to learn the stuff when you do the CPL's etc, what you did at school, as long as you weren't at total dullard, is irrelevant in my opinion.