More than comfortable if you don't have kids and don't expect to have your own flat. I live in London, and probably spend around £1200-1500/month total. Which is more than what some of my friends earn.
That amount in London is a bit of a problem if you live close to the city center due to housing prices. So you can either live close, not having the overhead of commutes, or live far away and then be better off financially but have the inconvenience of a commute.