Food
British food is terrible! This is a World War 2 rumour that just won't die. Food back then was terrible, granted, 
but it's been good for some time now - see the food section on this site for confirmation.
There are numerous supermarkets, many of which have branches around central London. Sainsbury's and Waitrose are generally more expensive, but have the classier food. Tesco, Asda and Morrison's are broadly, more budget options.
It's generally accepted that London is one of the best places to eat out, anywhere. I recently read a blog commentary where one of the authors of 'Freakanomics' was trotting out the standard incorrect assumption of the adventurously-challenged. That London had the odd decent restaurant but was still an epicurean wasteland. The comments were legion and beat him into submission. He sheepishly admitted that he hadn't actually tried that many places, so perhaps had been sweeping in his assessment. True.
Hardens, Time Out, Top Table - are good reference works - or you could start here on the Inside Guide to London. The food is good. Second World War rationing is a distant, foggy memory for peoples' grans and nans.
