In 2018, the UK amended the Misuse of Drugs Regulations 2001—not the 1971...

https://delta-wiki.win/index.php/What_Does_Marketing_Authorisation_Mean_for_a_Cannabis_Medicine_in_the_UK%3F

In 2018, the UK amended the Misuse of Drugs Regulations 2001—not the 1971 Act—to allow certain cannabis-based medicines like Sativex and Epidyolex by prescription. These remain Class B drugs, prescribed only by specialist doctors under strict rules