littleflyer,
All the people I knew who joined the air cadets loved it. After all, it's free flying - and you don't get a lot of that! Why do you think it would be a bother?
I don't think you need GCSE physics in the sense of anybody requiring it, but I think trying to do the ATPL exams without at least that level of understanding of physics would be pure hell....and that's an understatement!