UK cannabis law changed in 2018 through the Misuse of Drugs Regulations 2001,...

https://dlf-ne.org/what-international-treaties-affect-uk-cannabis-law/

UK cannabis law changed in 2018 through the Misuse of Drugs Regulations 2001, not the Misuse of Drugs Act 1971. This update allows specialist doctors to prescribe certain cannabis-based medicines, like Sativex and Epidyolex