I think the mortgage is around £1000/month. Rent would probably be more like £1300. The house is a 3 bedroom mid-terrace with a small garden in a good area. We're in S/SW London, somewhere in the middle of Sutton, Croydon and Mitcham (some not very nice areas there but it's nice here, honest!). We're an hour's commute into London but it involves several changes and some unreliable trains.
Before we moved we were in a decent sized ex-council 1 bedroom second floor flat (balcony, attic space, nice areas around) with a mortgage of around £800/month. It would have rented for about £900/month. There, we were still an hour away from the city but it was a short bus ride to the Northern Line so it was an easy journey, if busy.
We're in the position where it would be cheaper to live away from London but OH works in an industry where you need to be in London really. The other possibility would be Edinburgh but that's about as bad.
I'm Northern too and prices here are just bloody stupid. My mum rents out the 5 bedroom family home in a great area up North for less than we would spend on a 2 bed!