There is no official UK government cannabis card. Access requires a specialist...

https://wiki-tonic.win/index.php/Who_Regulates_Prescribing_Standards_for_Medical_Cannabis_in_the_UK%3F

There is no official UK government cannabis card. Access requires a specialist consultation and a review of your medical records for a prescription. Once prescribed, an optional patient card serves as useful proof of your lawful treatment to others.