The problem with the age verification requirements is that there are so many implementations.
Some require access to credit card, some used Simcards, some use (allegedy) independent companies, some require copy of driving livencr or passport.
I tried one that used a selfie to estimate age but it failed as it could not tell if it was a live photo (as far as I know I am still alive).
I tried Simcard verification and every one failed.
Even if you get verified after two hours of struggling, they then expect you to set up accounts.
I am not prepared to use credit cards, driving licence etc - The potential security risks, AI fraud etc is ridiculous.
So you now have hundreds of sites with different mechanisms, with extremely dubious privacy/security.
The only practical short term solution is a VPN!
The UK Government should have setup some kind of secure system where a person registers (they do it for Tax already), and you are given some sort of secure code that you quote - this could be a rolling code.