Do you live in your own place at the moment, or with parents? If you're renting anywhere, you'll need a deposit to put down (I only had to put a month's rent down on my flat, but when I was looking at other flats through letting agencies, many were asking for two months' rent, plus money for a credit check) - London's going to be pretty pricey, as you probably already know - and if you haven't already got work sorted, you'll need money to tide you over until you do get a job. Also bear in mind that you'll probably need to travel down several times before moving to go to interviews.
www.fish4lettings.co.uk is good for rented properties all over the place, and
www.jobcentreplus.gov.uk or
www.fish4jobs.co.uk are good for finding work.