Hi
I've just graduated from KCL. I completely understand your worries so let me offer some advice.
What course will you be doing? Some courses group cohorts together for first year so that might help with making friends.
-You'll definitely find people who don't go clubbing/drink etc, I would recommend just chatting to people in lecture halls- the usual where are you from, what alevels did you do, are you excited about the course etc are good icebreakers. You could always ask to tag along to classes or ask if they would like to go explore the campus.
-KCL offer events for those who don't drink that typically run in the afternoon and there are events that run throughout the year that you can buy tickets for.
-Your personal tutor will also have several other tutees and will most likely invite the whole group for your first meeting so you can chat with them too.
-If you have any hobbies or feel like finding a new interest then join a couple of societies to find people with similar interests.
I lived in halls during my first year, and while I quickly became friends with my flatmates I found myself closer to those on my course. When I lived at home (during lockdown) I made a few friends by attending on campus sessions and staying on campus a bit later to chat/catch up with people (of course, when covid restrictions allowed for this).
You'll meet a few people in first year but you might not speak to them when it comes to your final year and that's completely fine, just enjoy freshers week by doing what you're comfortable with.