Two absolute prerequisites:
1. Extensive and diverse
work experience, on which you can give good
reflections, firstly in your form and secondly, if you find the chance, at the interview. This might make the difference in the end.
2. Good grades, in both your A levels that must include Chemistry etc and your degree. There is no admissions exam, and precisely for that reason they will look out for strong evidence of academic strength and motivation.
What is also useful to know:
even AFTER the interview they will still also take into account your application. I don't know how much weighing is given to each component but I do think the application (especially the separate form you have to complete) is important. As for me, I might have done average in the interview (70 interviewees, so somewhere among 30-40 best/worst, depends on your perspective ...) but I put in a lot of effort in the application form which might have shifted me to the lucky 24 or 26 who were given offers. I gathered diverse experience and thought about what I gained from each a lot, keeping diaries and a whole blog on it and discussing it with clinicians, family and friends. So I volunteered in a Tanzanian clinic abroad for a month last summer, collected surveys with cancer patients (speaking with individuals for hours) for a year, shadowed doctors in the UK and Italy, volunteered in a hospice in Italy and now work as full-time healthcare assistant in the NHS.
The interview is slightly challenging, it's not vastly different to other med schools but they do want to see how you think. I was completely clueless at one of the stations and did not do that well in others, I made informed/smart guesses and justified them and that is what they probably liked. If you enjoy intellectual discussions, be it on science and/or ethics, they will see it, even through the veil of your anxiety. I thought I had appeared too insecure, as all my fellow interviewees looked very confident, but perhaps it was fine. They must also have liked some of the personal examples which I mentioned in my answers.
Yes, read all of the ISC book in a more leisurly mode. Then compile a catalogue of questions and try to answer them, perhaps take notes for the most important ones. Read a lot about medical ethics, google stuff, use the GMC guidance, borrow a book. Keep up with the news, read a few articles on the NHS (google "NHS" and go to the "News" tab and pick a few articles) every day or every other day. Make summaries of those you want to remember and skim the summaries together with your work experience diaries and question catalogue every now and then and in the last days before the interview. Try the practical station type of questions with yourself. Watch videos of consultations on Youtube as several medical schools make you comment on them and also generally do some research what constitutes a good consultation: verbal and non-verbal skills, structure, etc. And if your course is academically rigorous/very sciency, make sure you also keep your scientific mind busy by reading reviews or whatever on topics of interest.
Hope this helps!
Best of luck to you all!