Tipping in England:
Tipping is becoming much more appreciated in the UK especially in these very tough economic times. Most people who work in these jobs are struggling very much at home and a few quid here and there can make a huge difference. UK workers still get most of their money from their wages but with inflation these wages don't tend to cover rent/food/petrol so well these days so a bit of spare change can mean a lot.
I'm not American, I don't class myself as a foodie, (just someone who loves to eat) however I was born and bred in London so I'd thought to pass on some advice from a different point of view.
The only time its not easy to get around is during the rush hour. This is why from my long experience I would recommend you look for place in a good commutable distance from your place of work first! If you are not walking you want to be on a single tube line, trust me interchanges are a pain. For the stations you listed you want to have easy access to Jubilee, Picadilly, Victoria or Bakerloo Lines. Secondly you want to bare in mind the London Zones. For each zone you cross on a tube map the more expensive your ticket (and the longer your journey). Zone 1 accommodation tends to be very pricey as its the most central location and full of shops, businesses, offices and hotels rather than housing. At all other times its easy to get around the capital.
London is full of markets. The most famous are Borough (general food), Billingsgate (fish), Smithfields (meat), but here's a link to a website guide listing quite a few:
Restaurants: As a general rule in London if you want to eat a particular speciality eg Indian, Chinese and you want authentic, look through the window and see who is eating there. If you see Indians eating in an Indian restaurant it's usually the real deal. However lets not completely knock the British/another culture crossover which is a whole wierd foodie concept of its own (e.g. that great British institution that is the Chicken Tikka Masala). Areas where the initial immigrants settled tend to have the best ethnic restaurants eg Brixton for Afro-Caribbean, Bangladeshi in Brick Lane. Restaurants come and go so much in our capital that I would check out online recommendations to see where's hot at the moment such as TripAdvisor and Time Out. We also love our fads, we had the Thai, the Sushi, the Tapas and at the moment it seems to be Brazillian.
Last thing I don't know how long you are in London for but we do have a annual Taste of London Food Festival which is amazing, no other word for it.