For vintage, last time I was in London in 2019 I really enjoyed my visit here. Nice people. https://antiquewatchuk.co.uk/ I just wandered in off the street but it looks like they're now appointment only.

I have fairly skinny wrists and grew up in a time when men's watches were commonly 34mm or so; to me, nothing over 38 looks right on my wrist so I don't go any bigger. But that's me -- you're you, and as others have said, you should wear what YOU like and feel good about.