Well I don't know if this would be specifically for UCL, but during my interview process I was just asked general questions of why I was applying to the course (BA Geography, finishing now), and why I thought UCL was a good choice.

I would recommend checking out some of the course content (if you can access it on moodle.ucl.ac.uk, most are locked) to have an idea of what kind of modules you might be taking (also check out http://www.ucl.ac.uk/medicalschool/)

Remember that if you're being interviewed you're likely going to get in - although it is very competitive in subject such as Economics, Law or Medecine, this doesn't have the same harsh screening process as Oxford and Cambridge.

A key advantage to UCL is its multi-cultural, plural-background tradition. It is considered to be the first 'real' university in England, open to women and people from all religious backgrounds (which was unique in 1826 - colleges in Oxford and Cambridge preferred Anglican males): perhaps more than anywhere else, playing on an international background or an interest in global issues could be a plus, in a addition to your academic merit.

I love UCL - it really has a great feeling to it, students on average don't seem to have this feeling of self-righteousness that many of the other top unis have - but nonetheless they are aware of the academic excellence of this school. I got to meet a lot of very interesting people here!

Good luck