Cman,
It really depends what you are in the country for. If you are going to a show or heaven forbid have to work i would try to stay local to the venue and travel into the city for site seeing.
If on the other hand you want to come and marvel at the wonder our little capital has to offer then i would recommend the following areas:
Westminster (SW1) - Nice near the main stuff Houses of Parliament etc..
Kensington - (SW7) - A bit further out of town but still nice, probably a taxi to town or get the tube.
Trafalgar Square area - (WC2) - Good for theatres and covent garden (usually rammed with skirt) slap bang in the good stuff.
My choice would be WC2 as it's close to all the night life, if you do go avoid some areas of Soho (red light/porn district). It can be dodgy especially late at night if you are alone, some good strip clubs around though.
As with most places though, if it looks shit, it probably is shit.
A good place to do some window shopping is
http://www.laterooms.com/en/region108.html
it at least gives you a price guide (note they are discounted there due to short availability) and area maps etc. I usually prebook with a hotel then check back a few days before i travel and if it's better rebook through them. I saved £55 on one night last month in Manchester that way.
Dunno if thats any help, if you want more specific information just ask. Sorry to be a bit vague but i have always crashed in peoples apartments in areas like Islington and Kensington so have never really had to do the hotel thing in town.
