I returned to the north west from north London two years ago. Although originally from Cumbria, I'd spent a few years down south, and had been living in Enfield for about 5 years. My girlfriend and I just got fed up of London, so we upped and left. We moved to Lancaster (well, a village just outside). I had been working in medical research in London, but I got a totally different job up here. And, funnily enough, I actually earn more up here than I did in London.
Lancaster is a good base. You can easily commute to Preston, Manchester or Liverpool, and it's a great base for both the Lake District and the Yorkshire Dales (and the Forest of Bowland is literally on your doorstep). I can be in the heart of the dales or in the Lake District in 20-30 minutes. No more long-term planning of trips: if I wake up and the weather looks good, I just throw my kit in the car and half an hour later I'm walking the fells.
We have absolutely *no* regrets about leaving London, and I don't miss it at all. The only regret we have was that we could have (and should have) left London a lot sooner.