Bazzer,
I'm about six years in front of you and followed almost the exact same course that you're looking to take. GCSE's, A-Levels, Aviation Degree, Florida PPL........etc. Now working in aircraft engineering.
The other guys are right, it's probably best to do A-Levels in subjects you'll get better results in.
Apply for every scholarship, not just BA. Even if you don't get them, It's all good experience.
T&S