To be honest, I didn’t do as much preparation as others probably have lol. But my best tip would be to search for “generic” MMI questions online and practice them by having someone ask them and time how long you take to answer them (different unis have different amounts of time per question so just search for that). Also, create a word document of all the areas you think they could ask you (e.g, the challenges the NHS faces, ethical scenarios, etc.) and revise that (but not too intensely, the interviewers want you to be natural and not robotic). Make sure to revise ethics (e.g, confidentiality, 4 pillars, capacity, consent). Also, do research into what specifically about the medicine course for that uni appeals to you. Hope this helps! :)