It is an issue of national sovereignty because the UK is trying to force foreign civilians to enforce their laws outside of their jurisdiction for free, by way of bullying, threats, and illegal fines.

What the UK does within their own borders is their business. They don't have any right to force foreign entities to censor themselves or tl block UK citizens, as if that's even a technically feasible request.

The UK's free speech situation is bad, yes, but that's not the problem we're talking about here. The matter at hand is the UK trying to censor free speech by foreign citizens outside the UK and is using illegal threats to do so.

This is all theatrical. They already know that what they want is a section on what can be see or not within its borders. After this case has been processed and maybe some others some genius will say that internet should be a subset of the whole internet. That's nothing new. For years during war times the post office had followed letters from and to specific destinations/people for conference.