What are the best London neighbourhoods to live in for under 850 bp per month?

I'll be moving to London in May 2010 and after reading some online material decided on a budget of around 850 BP per month to rent a studio or 1 bedroom with appliances like washer and oven. Is this realistic? Which neighbourhoods would be the best to live in considering the desirable commute is under/around 30 minutes to heart of business district in city of London. Should also have easy access to grocery shops, bars and above all tube stations. I don't mind changing tube lines but would hate to take a bus and then tube. How much are typical utility bills per month for 2 people? Which websites are best to search for rentals? Also why are all rents quoted per week and not per month? Is that normal? Thanks for your comments in advance!What are the best London neighbourhoods to live in for under 850 bp per month?
I would have a look at the nicer areas of North London , not South London. The first answer has given you some of the worst areas.What are the best London neighbourhoods to live in for under 850 bp per month?
Brixton, Peckham or Hackney.