Of course it can be shown on any of the main five channels, but they'd probably be too scared to show it! All UK channels are generally bound by the same broadcasting rules, and if it doesn't breach those regulations then it's up to the individual channel to censor or not. Obviously, if it was on ITV, they would show it at 3am and each episode would be cut down to about 10 minutes!
It would probably survive uncut for violence and nudity, but it could be censorred for profanity. Every episode is littered with many f and c words. It is really wel done.