I imagine i would be based in London if it's the busiest
Well you might initially be elsewhere but a transfer to London base won't take too much time. You might want to do some research into rents and house prices... Most people don't quite fathom how expensive it is, including outside the M25 (Gatwick, etc.). That said you could probably find a cheap place in Luton, but it's a bit scary :-)
You'll have a lot more money left in the bank up North.
P