Since Nov 2018, medical cannabis is legal in the UK via specialist...

https://wiki-global.win/index.php/What_are_Cannabis-Based_Medicinal_Products_in_the_UK%3F_A_No-Nonsense_Guide

Since Nov 2018, medical cannabis is legal in the UK via specialist prescription, usually after other treatments fail. While technically accessible on the NHS, it’s rare; most patients use private clinics