Hi Jemma, I had an interview at Uclan in March and I have accepted a place there. You should get a letter with all the details of what you will be doing on the day. It was a written test followed by a talk by a tutor, then lunch, then interview. The good thing about it is that they let you know on the day if you are successful.
I found it to be pretty relaxed, tutors seemed OK as did the other people on my interview day.
As for the questions you just need to have a broad knowledge of what it is that social workers do and issues surrounding social work. It may help to brush up on your current affairs. Also have a clear idea of why you want to study social work ad be able to put it into words for the interviewer.
Good luck!!