You'll need fairly speedy mental maths, but if you're capable of achieving A* in other subjects you will be able to improve your mental maths skills to a level desired by flying schools and to a level expected/required in a commercial operation.
Have a search around on PPRUNE, as there are a few websites that will be able to help you improve these aspects.
You will also need to have a sound understanding of GCSE Science so that you can pursue the ATPLs without many issues.
Hope this helps.