Enforcing any sort of punishment outside of their jurisdiction is going to require the cooperation of the country where the website is actually based.

Now, countries do often assist each other in law enforcement, but in a situation like this it's most probable that the host country will simply check to see if the website met their own standards of due diligence in attempting to comply with UK law- which would probably be simply blocking all traffic from the UK.

I can't see any country requiring their website operators to employ expensive and sophisticated technology to attempt to suss out whether or not a connection is a VPN and whether or not it ultimately redirects to the UK. They have a vested interest in the economic success of their companies, and they are not going to make them take unreasonable measures to comply with obtuse foreign laws.