English: I'm a well known English pedant, but personally I found CrescentPirate's original post easily readable; he does have the rather odd writing signature of using the consistently lower-case "i" when "I" would be correct, but it's the only consistent error and didn't detract from the readability of the post.
Maths: Personally I really think (CrescentPirate) that you need it. Not necessarily to handle the maths components of ATPLs, which you've almost certainly covered with your physics GCSE (unless the syllabus has changed a lot since I did my O levels anyhow), but because most HR departments will not consider employing anybody in a professional job without both maths and english GCSEs. Additionally however there's a strong chance that you'll need to enhance your mathematical reasoning skills in order to handle, for example, W&CG and nav subjects - and studying for and passing your maths GCSE is not a bad way of developing that reasoning to your own benefit before (or whilst) getting on with your ATPL study.
G