The UK instructs ISPs to block access to deliberately non-compliant sites, however users want to make connections to the sites and those sites want to receive connections to those users. VPNs will be effective in allowing access to non-compliant sites as long as ISPs can't identify the VPN traffic.
Of course, the British ISPs can initiate the tactics used by China to identify and block illegal traffic. However there are limits to this. Unlike Chinese users, British internet users regularly make connections to international servers so various bridging techniques are possible. Like VPNs, proxies or even Remote Desktop.