The first part is a technical question and the second part a definition one.

For the how to: the most common approach is to simply blacklist their IPs on a provider basis. This leads to no provider that obeys your blacklists to allow their users traffic to that target. Usually all providers in a nation obey that nations law (I assume, I only know that for my own :D)

For the censorship: I don’t like that word because it’s implications fan be used against any and all laws. A shitload of content is made inaccessible because it breaks laws from active coordination of attacks to human trafficking. All of this can be described as censorship.

Forthe UK law it’s… I’m not British and to me it appears to be a vague tool to silence and control all types of content under the guise of protecting children. Not with the intention to protect or prevent something but with the intent to control. I would fully understand and emphasize with using the word censorship in this context.