In the UK there's less of a distinction between stage acting and screen acting. Which means you'll find a lot of popular British actors you see in TV started out being classically trained in theatre. That amounts to another skillset that increases the actors range. Big name British actors will go and do a run in West End show and my impression is that doesn't usually happen as much in the US.

In addition, yes, I would say that overall, British TV is less focused on finding perfectly attractive models. There's still an attractiveness bias but, even hot British actors are still a person you could believably see walking down the street. As opposed to like CW shows who I assume are grown from a vat somewhere in a lab.