If you are going to have to live in London on the same dosh as you are getting up there, you would be radio rental to move ... renting a bedsit will cost you the same as you would pay up there for a house !!
Seriously, if the wedge is the same, stay put and wait for a better package .
For the rent I pay for this flat I can still get a decent enough pad down there, not as big or across the road from work like this one, but nice all the same. Its more money down there but no car included. Pension isnt as good either, but I'm 26 and might not get to becoming a pensioner anyway!!
Going down next week to have a look about. The feel of the place and transport links etc might be key. There does seem to be decent opportunity for promotion, and a bonus, if I put the graft in. If I like the job as much as I hope I will then I wont mind doing that too much. See out the visit pans out I guess.