The UK already has libel laws that are more vigorous than those found in the US. If those laws aren't comprehensive enough, they can pass new laws prohibiting the dissemination of provably-false statements. Arbitrarily shutting down a contrarian media organization is not the answer.

Your response that it's ok because "it's Russia" reminds me of a story that I heard. A man asks a doctor whether it's ok to pull the legs off a spider for amusement, and the doctor says it's not. The man asks why, since the spider isn't capable of feeling any pain. The doctor replies "I'm not concerned about what will happen to the spider. I'm concerned about what will happen to you."