There is no official government medical cannabis card in the UK. Access starts...

https://wiki-site.win/index.php/What_is_a_Medical_Cannabis_Card_in_the_UK_Supposed_to_Prove%3F

There is no official government medical cannabis card in the UK. Access starts with a specialist consultation following a review of your medical records. If prescribed, you may choose to carry a private card as optional proof of your lawful medication.