In 2018, UK cannabis law changed through an update to the Misuse of Drugs...
https://yenkee-wiki.win/index.php/Why_Are_Most_Medical_Cannabis_Prescriptions_in_the_UK_for_Unlicensed_Products%3F
In 2018, UK cannabis law changed through an update to the Misuse of Drugs Regulations 2001, not the Misuse of Drugs Act 1971