One tweak to the rules and all of a sudden not only do porn sites have to verify the age of their UK visitors but also anyone connecting from something other than a residential ISP.
The more troubling thing about these laws is enforcement. The threat of fines only works against websites that map to a business entity. For anything else there will surely see a ramp up in the size of The Great British Firewall Ruleset, edited by the courts, and distributed to the Big N (5?) ISPs.
What will become of the smaller ISPs that refuse to block illegal sites?
It's conceivable that a VPN provider could change the V6 IP on their server every hour for the rest of time and still get unique addresses.
If the VPN server only has an IPV6 address and no V4 address, can they connect to the target website?