I did a Surrey interview last year and got an offer. It is prerecorded so I think they're looking to see how you think and approach a question, and how well you are able to discuss it and formulate an opinion on the spot (though they won't expect you to have a rehearsed opinion). I found it was more just talking through ideas as they came to me, but don't be afraid to take a moment at the start and throughout your response to organise your thoughts.
Also expect the unexpected! Practise your skills in answering on the spot questions and presenting your ideas on it for 4 minutes - there is no point in rehearsing answers for this interview. It is quite enjoyable when you get into it, view it as a chance to explore your own ideas.