You're looking at this in a "grass is greener" way.
I went to uni traveled, lived and worked in different countries, had a career etc. then got married at had DC in my very late 30s.
I keep in touch with less than a handful of friends from uni. And that is the odd email or text. Hardly ever see any of them now. You tend to drift apart within the first few years of leaving uni. As for school friends. Well it's now so long ago I keep in touch with two, Christmas cards.
And even having DC later on means a few friends drop you when the babies come along.
As for uni. You can still go now. No reason not to besides you're hardly old.
Go part time and just make sure it's a good course worth doing which will repay its worth later on. So many at 18 choose random courses because they sound "fun" and end up saddled with debt and a useless degree (and can't afford to start a family).
You will still be able to travel. Take your DC with you. Granted you won't be able to party your way through Thailand but tbh very few people over the age of 20 would enjoy that anyway.
The world is still yours to take on. You've not missed out on anything yet. You're just doing it the other way around.
Having DC in your late 30s isn't always a picnic. You're derided by some midwives as being "high risk" and a burden on the system because you waited and did all those other things first. And it's absolutely bloody knackering when you're older. I think back to being able to stay up all night at 21 but suffering badly with broken sleep with the DC (they are 5 and 3 and I've not recovered yet).
Besides being out partying when young doesn't lead to happiness. Sure some of it was fun but some of it was filled with heartache and problems (he said/she said drunken misunderstandings etc etc).
Plan ahead. Start looking at those uni courses now and when you're DC is settled at secondary, go and do it.
And if you don't want any more DC, talk to your partner. And if you do, it still shouldn't stop you doing anything in the future.