I think you'd do well to heed the advice given by Re Heat.
I'll relate it to my story.
Always wanted to fly. Went to RAF at 16 with GCSE's. Told to go away and come back at 18 with A Level's. Went back in my final year of A Levels to get the ball rolling when I was told " Your chances of success at 18 with A Levels are much less than the guy next to you with 3 years at Uni and a degree"
Fair point at the time and looking back on it, no matter how mature you think you are, you always have a bit further to go.
So my dilema is Uni (which I didn't want to do as it meant 3 years less flying) or go for RAF anyway.
I went for Uni. Did Physics "because that'll help you being a pilot"
Hated every minute of Uni. Physics degree does not even compare to A Level (being in a large theatre with rambling lecturer that you don't want to stop mid flow because you can't understand something was a big jump from my A level class with 6 of us sat round a table with a great teacher)
Joined the UAS and was persuaded to apply for a Direct Entry scheme. Got selected but in order to get in, needed to go back for a further medical over the period of my exams. Which meant failing them, but getting a job. Withdrew from uni, worked to pay off a year of debt, then joined RAF.
If I had to give advice to someone in similar shoes, I'd say pick a degree / subject that you like, not one you think you'll need. There are many pilots in the RAF that did degrees such as Music and Art. Always have a fall back option and never underestimate the maturity that living on your own / travelling gives you.