There’s no official UK government cannabis card. Access is prescription-first...

https://wiki-burner.win/index.php/What_happens_if_I_do_not_have_the_right_documentation_for_medical_cannabis%3F

There’s no official UK government cannabis card. Access is prescription-first via a specialist consultant after reviewing your medical records. If prescribed, you can opt for a private clinic card as optional proof of lawful use for police or employers.