You could always go to college to get a better GCSE Maths (don't bother with foundation level). I wouldn't worry about A levels too much.
The entry requirements are presumable for an integrated course, so this might be a bar. However going modular you are unlikely to find such restrictions other than how big a cheque you or your Dad can write.
They are lots of commercial pilots out there without a good GCSE Maths grade, so I wouldn't worry too much at this stage. HOWEVER the ability to do basic trig, ratios, manipulate formula, distance/speed/time calculations to name a few will be VITAL.
Some of the schools even offer maths & physics revision courses/DVDs prior to attending the main ATPLs, suggest this might be a better option.