Go for one that best matches your interests! You'll have some optional modules and it'll be best if those will suit your interests. For instance, you may find you wanna do Educational but maybe your uni doesn't have any Educational modules. Also, if you have a clue about a certain path you'd be more interested in (e.g. Clinical, Forensic, Health, Organizational), then it would be helpful to choose one that offers a Masters and/or a professional doctorate and/or a PhD in your area of interest, cuz you'll get lots of people specialized in that area for an elective module and also, if you do an MSc in the same place, you'll get cheaper fees.
I know UCL has a great department, I believe King's dept is good too (check their Masters to see what areas they excel in). And I think I heard some good stuff about Goldsmiths too? That's only for the London unis, there's fab ones outside of London too ofc, like Bath.
In Psychology, I'd say it's more about having a department that specializes in your specific thing, it'll make things easier. If you're not sure yet what you wanna do, just think of which area you'd like to do most, or at least you think you'd like - neuro, social, developmental, cognitive.