Have you looked at the RAF Recruitment website for all the entry requirements? Don't forget there's health standards to meet, as well.
No point in 'aviator school', or necessarily Uniformed Protective/Public Services; you need UCAS points and you don't need to learn about flying when you'll do that anyway, if selected, and problem-solving and leadership etc can be developed through any number of hobbies and interests, part-time job, sports.
You should get qualifications that you can use for an alternative career if you don't get into the RAF. Always have a back-up plan.