London - salaries, cost of living etc?

For a few weeks I have started thinking about moving from the US somewhere closer to my parents. I suppose I also miss a bit the European style of life…and the food!
So the first choice that came to mind was London. I know that it’s supposed to be an expensive city, but usually where you have higher rents you also have higher salaries. Plus NYC made me really appreciate the diversity that a big city can offer.
So I figured perhaps someone here could tell me more about it. For example, what is a good salary in web design (or UI) there, rent cost for a decent 1br in a decent area of London(and what those areas may be), how much do you usually spend on food, bills and transportation.