Hello, If I were you I'd go and stay in one of the St Christopher's Village Hostels ( part of Belushi's Bar) in either Camden or South Bank for a week to see if you like London first before you up sticksas it's cheap accomodation. Whilst you are there you'll get a taste of what living in London is like (I like Camden, think it's great, but not to everyone's taste. If you are young and looking for parties, nightlife etc it can be great, just be careful as in any big city with people you don't know).
It's not like a homeless hostel btw, it's just very basic accomodation for travellers attached to Belushi's Bar. Once you are there have a look around, buy LOOT, for rooms, flatshares etc and see what happens.Excellent advice from Nat and China about live in bar work. If you dont like it Liverpool and Manchester are nice cities and a bit cheaper rent wise.Good luck:)