What does it REALLY cost to live in London?

I am considering a position in London and trying to figure out what it will really cost to leave there.  My co. will provide some additional compensation to cover the higher costs, but I'm having a hard time figuring out if it will be enough or if I should negotiate for more.  For example:

1) What does a flat really cost?  What are good neighborhoods to live in?  My minimum requirements are:  1 bedroom flat, furnished, clean, in good repair, decent/safe neighborhood, close to tube (as I don't plan to have a car.)   I've looked at a lot of adds on line (foxtons.co.uk mostly)  but I'm not sure which neighborhoods are good. 

2) I keep hearing 'it's expensive'.  Can anyone tell me how much more they pay for groceries, clothing, etc.? 

Any help you can provide will be greatly appreciated!

Thanks!

I'm looking at a 2-bedroom flat near St John's Wood...a very nice neighborhood for a roommate & myself...we're probably going to spend around 1350 - 1600 pounds per month.  And then there will be the counsel tax which is at least another 100 pounds per month each.  From what I've seen on this board, clothing is very much more expensive than in the states...I'm buying most of my clothing in the states before I leave & when I visit.  Groceries - about the same as any other big city (I lived in Boston before this).  Other expenses - a tube pass is VERY expensive if you get a monthly or year pass...I think a year is around 900 pounds for 2 zones & the monthly around 90 or so. 

Good neighborhoods (from what I've been told & where I'm looking...I'm working in St. Johns Wood so I've only explored near there):
- any of the Hampsteads, some parts of Islington, Maida Vale, Bayswater, Marylebone, Notting Hill, Primrose Hill, Regents Park, Kensington, Knightsbridge, the new sections near Canary Wharf.  I'm sure there are many other good places but those are the ones I've heard most about.  Another place to look is on Loot.com for pricing.

You might want to hook up with a relocation agent (it's what I'm doing).  You can give them an idea of what you are looking for & they'll help you out.  You might want to ask your company to pay for this.

Best of luck to ya!

All the major supermarkets have web sites. You can go on there and price the kind of things you like to buy, then compare to what you pay now. The big ones are Tesco and Sainsbury in London I believe.

I have found that flats that are advertised on Foxtons seem to be a bit more expensive than it's possible to find through other sources.  Try this one:

http://www.findaproperty.co.uk/index.html