No, they should block with a very visible message, tailored to the british public. I know what that status message means, you know it, but the general public doesn't. They need the black page with big letters they used before with sopa/pipa/etc.

You can return a 451 error with a descriptive page, same as how sites have custom 404 pages

We need new 6xx codes. "Requests that are fine, need no redirection and have no errors but are blocked because of politics, overbearing laws or regime"

That's what 451 means.

It's "user error, you are trying to access the site from some dystopian society that prohibits it".

Yeah but I want to know if I should submit, protest or revolt. I need more codes :)

451 is such a good reference though, other codes just wouldn't be the same :(

My scheme allows for 666 but I get it.

The 451 response's body will contain further instructions.

I guess. But I'd like to grep my access logs to get some high level metrics for the uprising.

For example, "An HTTP Status Code to Report Legal Obstacles":

https://datatracker.ietf.org/doc/html/rfc7725