My 2 cents on this is simple - go to university if the job you want to do requires a university degree. IF it doesn't, don't go.
This doesn't change if you want to fly. IF all you're looking for is a job to pay for flying, seriously, learn a trade. If there's a job you'd like to do AS WELL as flying and you can't really decide, then maybe uni. All in all I don't think many people should be heading off to uni at 18.
When I was at school as others have said, everyone was going to uni, you were basically that dumb kid if you weren't at least applying. I had NO idea what I wanted to do, having become too tall to fly. I had a weekend job in macdonalds, and I'd got myself put in charge of kids parties, basically so I didn't have to work in the kitchen. It was easy and I was good at it, so I thought "eh I could probably be a teacher" when everyone was applying and off I went to spend 4 years becoming a teacher. Of the 30 people I really knew on my course, today 2 of them are actually teachers. Of my wife's 6 closest friends, only three work in the field they went to uni for 10 years later.
It's not the debt. If you live in the UK it doesn't really matter. Honestly by the time the government add another tax to your pay check, it's such a small payment you won't notice it. It's the time you waste.
If I could do it over, I'd have chosen electrician. Sure I don't think I'd have stuck with that either, but I'd have been a lot better off. Ultimately it took me 6 years out of university to find my passion other than flying - programming. If i'd known that 15 years ago, sure I'd have done that at university, but I didn't and really I shouldn't have gone.
Don't go to university for a fall back. Go to university to get the job you want. If you don't know what you want now, the student loans comany will still issue you a loan when you're older .... if you've not used one before.