London is a fantastic city. Contrary to the comments made earlier, British citizens make up around 80% of the population, black Brits (around 10%), asian/indian Brits (around 12%) and white Brits (around 60%). The other roughly 20% would be non-British. As far as for Londoners all being rude, I could also generalise and say that they are all fabulously welcoming. As it is, and as I am sure you are aware, you'll probably find that people are people as much as they are in any western city.
I'm not sure about where to stay that would be affordable, although if you choose to stay away from the centre of town, you'll find cheaper accommodation.
As for touristy things to do.....first the obvious, if you haven't seen the
Natural History museum, or the
Victoria and Albert, then you must. These are fabulous museums and are beautiful as well. Both are in South Kensington. Check out
Camden Market (mainly clothes and music) on a sunday. It's buzzing. Also
Spitalfields market, great on a sunday (near Liverpool Street). For bars and coffee and people watching, go to SoHo, while you are there, check out
Madame Jo Jo's for some camp drag and cabaret, on Brewer Street. Take in some live music at
Ronnie Scott's on Frith Street. For art, try the
Tate Modern, and then from there take a stroll through the city along the Thames, go west and you'll end up near the
London Eye and the
Aquarium, go east and you'll end up at
Tower Bridge and the
Tower of London.
They're all quite obvious choices, so I hope they help you get some tourist inspiration!