It's not a full solution. I've seen UK sites that, following the Online Safety Act, simply require all users to verify their age rather than bother to figure out whether you are actually a UK customer or not. I guess it's easier to implement and many sites mainly rely on domestic customers anyway so they don't care if international users are affected.

Also, this isn't just about porn. For example, I can barely use Reddit now if I connect with a UK IP address: the merest hint that there might be some NSFW angle to a post is enough to trigger their algorithm into requiring age verification.