UK has limited enforcement options, of course, but it’s their sovereign right to prevent illegal activities and/or punish for them within their capabilities. This is why 4chan lawyers are asking for political response as if UK were a rogue American colony.
Seems likely. And then that won't work, and they'll tell ISPs to block VPN traffic too.
Even today NordVPN is in the #5 spot, above Uber and Google.
Their reaction puts on record the constitutional/legal barriers, preserves strategic optionality, and possibly preempts escalation that could still cause real headaches. It's strategic, not a sign that they actually think the UK has a case.
If they can be used in the UK, then the same general principle applies here as with pirate radio and over-the-horizon artillery.
The attempt is unlikely to work, but with Trump who knows, so they will probably indeed tell ISPs to block it.