"As the Americans learned so painfully in Earth's final century, free flow of information is the only safeguard against tyranny...Beware of he who would deny you access to information, for in his heart he dreams himself your master. Commissioner Pravin Lal, 'U.N. Declaration of Rights' "
The thing is, in the UK, porn websites are already blocked by default by most ISPs and mobile networks. Only the account owner can unblock that content, either by calling the provider or by changing something in their account settings. And yes, you'll need to verify that you're an adult if you signed up to the service without providing them with details (possible with some mobile providers).
This has been the case for the past 10 or so years, so why exactly do we need this age verification stuff?