Hi everyone, me again. I'm in my final year at KCL and thought I'd answer my own question.
I'm so glad I picked London, honestly. If you want more of an insular student experience, I'd say St Andrews for sure, but it's (harder, but) definitely possible to have enough of that in London while still having the benefits of variety and opportunity.
If you want your life to be totally different, London is your place. There are people from all over the world, a billion different places to try a bunch of different activities, and you can sort of pick how different or similar you want each day to be. London universities and organisations also have way more opportunities for academic and career development. You're in the centre of the country, so when something big happens, you experience it firsthand. Mental health support in London is also much better - any university is going to be understaffed and underfunded in that department, but there are way more organisations and avenues for you to seek different types of help (for free / low cost), and the NHS is better funded and organised.
I have also visited St Andrews a lot and taken part in a lot of their student culture, so here are some positives about that:
- freshers is much easier. you're less adrift, it's easier to find your way around, and you don't have to learn to navigate as much at once. fresher's in London can be very, very stressful - but it is only temporary.
- the degree is longer. three years goes by way too fast.
- in a student town, you have an experience unlike any other where most inhabitants are a member of your community. it depends on how important that is to you. some people love it, some people find it claustrophobic. if you're not sure how you feel about it right now, just don't worry - it probably doesn't matter to you that much.
- you have way less to travel. it takes less time to get to lectures, to people's houses, to events. you spend less time on public transport.
- rent is still expensive, but much cheaper. your student houses will have much more space.
- for your first two years, you can/you must study other subjects. this is great if you're not ready to specialise. however, if there's only one subject you're really interested in studying in depth, England is better.
I wish I could tell 2018 me that I was going to be okay and not to worry so much - no matter what you pick, you'll adapt and get positives out of your situation. besides, nothing is permanent - if you really hate it, you can transfer. being a year behind is not as big a deal as it seems in school, and I can't even count how many of my friends have intermitted or changed course or university or derailed their lives to pursue something different (and it's absolutely been for the best). be honest with yourself about who you are and what you want/need, trust your gut, and relax. You'll be absolutely fine