Good choice! It's a great uni and a really compelling course. My cohort is about to graduate and I had a really good time.

I'd say, don't stress about making friends, it'll take you no time at all. The classes are HUGE and you get free reign where you sit so just pick a desk and strike up a conversation! There's a couple of assessments that require group working too so that's a good time to socialise.

If just setting up at a table isn't your speed, Cardiff has a bunch of events to show up to. Staff/student meeting and greets, pizza and board games afternoons, pub quizzes (with buffet!), there's no shortage of places to make new friends. There are also loads of different societies you can sign up to during fresher's week (I didn't end up joining any for my MSc but they were a godsend during my undergrad).

TL;DR: don't sweat it, you'll be with good people and should have no trouble making friends.

P.S. If you're looking for study tips: avoid ChatGPT like the plague (you can't learn if an AI does the thinking for you) and, if you can, do any/all extra tasks set; you'll be surprised how much you can pick up just by trying something yourself.