Depends on your budget I guess.
When I worked there I lived (albeit in some hotels) in West Kensington (nice and not too badly priced and very popular - great kebab shop too!
Was also in Hampstead and Belsize Park but stpidly expensive!
I was in Earls Court for a couple of days but it's really noisy there, constant sirens!
I have friends who live in Enfield and I like it there but the nearest tube is Seven Sisters, there are some nice parts round there though like Greenfields and such.
I found West Kent the easiest commute, straight on the district as worked on Ludgate Hill whereas the others I had to change.
Finchley and Golders Green are nice or Balham and Clapham down south.
Hve a friend who lived in Upton Park, noooooo!
Our receptionist was from Essex and she found the commute pretty easy.
Places round St Albans are really nice and quaint but depends what you're after really.