Hi, I've just checked with my son. He is now in his fourth year in Biochemistry and apparently speaking to his current tutor it would appear they've changed the formatting slightly for interviews since he's done it.
All he'd say is to just be solid on your personal statement and if they give it to you, any prereading, that's really the only prep you can do.
During the interview, don't be afraid to ask clarifying questions if there's something you don't understand about what they want you to do. And most importantly, just think out loud, tutors aren't always picking the best students on paper, they're picking who they want to teach and more often than not, that's someone who can articulate what they're thinking. Trying to avoid long periods of silence in an interview is good while still taking any time you need to think.
Hope this helps and good luck with the interview!