There's loads of unis that offer postgrad medicine (but as Democracy said it is technically still classed as an undergrad degree.) Just make sure when you choose your unis that you check your degree is accepted, otherwise you waste a choice.
E.g: Leicester GEP would not accept your degree, as they only accept healthcare graduates like nurses, physios etc. Warwick GEP would accept your degree, as they only accept biological and biomedical sciences graduates (so things like chemistry, biology, physics, anatomy etc.)