Hmm I don't know where I'm going to be working yet, and cost is secondary to other concerns. Things more important:

-Security: I must be able to walk the streets alone and be pretty sure my stuff is safe sitting in the flat. This could also rule out commuting if certain lines/whatever are unsafe.

-Accessability: being close to transport is obviously important but apparently the last tube runs at midnight and is often cancelled or dodgy. I don't want to be too far out so that I'm not running up large taxi bills after a saturday night out. Half an hour out of the city centre would be ok.

Thanks for the links