All rents anywhere in Europe worth living in 2015 are expensive - but London really is one of those cities in its own league.
Just to clarify a couple of things:
350€ is about £250
£400 won't get you a tiny one-room apartment without windows, that would be amazing! It'll get you a tiny windowless room, in a pretty grim house shared with 3 or 4 (or 5, or 6) other people, in an awful or really out-in-the-sticks location. (You can optimise by substituting some of the factors, but any way you slice it, a £400 room anywhere in Greater London is not going to be good).
Probably the baseline for a studio apartment (I've never seriously looked so could be a bit off) is £800-£900 per month for anywhere resembling a decent location.
Just to clarify a couple of things:
350€ is about £250
£400 won't get you a tiny one-room apartment without windows, that would be amazing! It'll get you a tiny windowless room, in a pretty grim house shared with 3 or 4 (or 5, or 6) other people, in an awful or really out-in-the-sticks location. (You can optimise by substituting some of the factors, but any way you slice it, a £400 room anywhere in Greater London is not going to be good).
Probably the baseline for a studio apartment (I've never seriously looked so could be a bit off) is £800-£900 per month for anywhere resembling a decent location.