Just Googled it and all I could find was the international ones and I don't think I could go on them since I'm a UK resident. Has anyone been on such things before haha? XD Any experiences??
The Royal Society of Medicine run a good graduate entry medicine evening.
Imperial does a medicine day, think it's fairly cheap if not free.
The Sutton Trust does a summer school, though you need to meet certain socioeconomic eligibility criteria, I believe.
Alternatively most, if not all, of the info you could possibly want to know about applying to or going to medical school can be found right here on TSR, if you're willing to take a bit of time to read the Wiki pages and sticky threads If it's actual first hand experience of medicine that you're after, speak to your local hospital about shadowing placements.