Romantic Hotel in London?

[Little Butch]

It's my girlfriends birthday in a month and I want to take her to London for a night.
I'm new to this relationship malarky, although I am getting the hang of it and am trying to impress.

We're both young (18 and 22), Ideally I'd like somewhere with a nice view, be in close proximity of some nice things to do in the day and maybe have a spa or something for her?

Budget's not massively huge although I do want to treat her.

Any suggestions?

[Little Butch]

Thanks, I was thinking more about £200 max though. I'd prefer to leave myself some pennies to spend in the daytime