The trouble here is that the law is so crazy that third parties allowing users in the relevant jurisdiction to access the site could result in the site still be liable, so then they would have the same reason to block your proxy service if a non-trivial number of people were using it.
To do any good you don't want to cause grief for the victims of the crazy law, you want to cause grief to its perpetrators.
Which would in turn cause the whole thing to be a farce, because then the solution would be for every site to geoblock the UK and then every person in the UK to use a proxy.
The problem here is that's what's going to happen instead of what ought to happen, which is repealing the law. And then some administration some years from now is going to stop ignoring the absurdity of it and decide to start enforcing the existing law against any subset of the ~everyone arguably now violating it that they deem to be wrongthinkers.
being unlawful is a vital tool for people to keep tyranny in check, I would hope that most people are incredibly strong supporters of lawlessness when the laws are wrong. To give an extreme example, I imagine you supported the hiding of jewish people during nazi germanys reign, which means you support unlawful activity as long as it's against laws that are against the people.
If GP is not a UK citizen and does not live in the UK, how would that be unlawful? They're not beholden to or subject to UK law. The UK's belief that they can enforce this law on non-UK entities is ridiculous.
Being silly to ridicule overreaching laws is top-trolling! Love it.