I agree with talkpedlar about the RAF. That route is about a career in the RAF and not a second option to anything.
I would say something similar about an aerospace engineering degree. You don't have sufficient fascination with the subject to get the title right, and aero-eng will cost £50k, 3-4 years of your life and massive levels of dedication to the subject. (And grade A or B A-levels in maths and physics).
G