Scarebus,
Like you, the sciences aren't my strong point, but I was given very good advice by the RAF Careers Office - they said "Don't do subjects you think the RAF would want - play to your strengths". This is because academic knowledge of science doesn't make someone a good pilot (provided you have a basic grasp ie GCSE), and also because, if the RAF turns you down, you have good grades in your chosen subjects to help you get a different job instead of mediocre science grades.
As a result, I took French, Latin and Greek A-level, got sponsorship for uni and read Classics, and here I am now flying in the RAF.
Before anyone else says it, Classics ain't much use in my day-to-day work (though I can be useful for a Latin grace at a formal dinner!) - but by the same token, how many ex-engineer students now flying in the military now use their degree studies either?!
Good luck,
TOTD