I believe the issues here are pretty obvious. University, especially in the UK is known for its drinking culture, the legal drinking age is 18.
However, shenanigans have still ensued, the first semester has been filled drunken trips to the chippie ending up in a hunt for the local red bull car, parties I can't remember and of course the dreaded 9am with a hangover. So, for those who want the TL:DR, at 17 you can definitely still have a great social life, just get other people to buy you booze and try find a group of people who prefer house parties to clubbing - and if you're in Edinburgh like myself, go to big cheese, it might suprise you to hear that it's not actually dead.
The social side of uni has been by far the best part, it's been 4 months but it feels like I've known some of my friends for my entire life and it's still surreal to me that I'm literally just living in a block of flats with 144(ish) teenagers/young adults, with the majority of my new friends mere doors away from my bedroom. So take advantage of this in first year! Have lunch, dinner, parties, study sessions, do anything you can with the people you meet and trust me it will make the lonely moments of uni much easier to deal with when you get a text from someone asking to hang out.
One of my go to things has been to organise collective cooking nights with a focus on different foods/cultures, we have had nights filled with pasta and garlic bread (and of course wine) where everyone helped to make different things, I made my bolognese which is now a party favourite, and we had a great time, it's a simple way to be more social especially around dinner which is when I would usually find myself alone in my room feeling a bit blue. It's also a great option for those who aren't a fan of heavy drinking, clubbing or loud social spaces as it's very laid back and civilised.
For those of you who are more drink inclined, well look no further than the classic gaff/house party. We would have one every Friday, and most Saturdays, it was a great way to end the week and being underage was no issue as other people could bring the drink for you, and because my flat was generally the host, I'd have the privaledge needed to steal some peoples' drink. It is simply the best and most straight forward (and most legal) way of having a great social life when you're under 18 at uni, and it works, even if people are going out clubbing later in the night you can still join them for pres which is generally the best part of the night anyway.
So, don't stop the fear of having a dead social life stop you from applying to uni at 17 because you can 100% make it work. Finding your group of people is the hardest part, but once you do you'll have a great time even without the club scene. Enjoy!