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

https://bizzmarkblog.com/is-cannabis-decriminalised-anywhere-in-the-uk/

In 2018, UK law changed the Misuse of Drugs Regulations 2001—not the 1971 Act—to allow specialist doctors to prescribe cannabis-based medicines like Sativex and Epidyolex