Hi! I'm about to start second year on the course.
Portfolio wise: At this stage I'm not sure, you'll probably have a Skype interview or go through clearing but prepare one just incase. What it consists of, I came from a Fine Art A Level background but everyone on the course has come from somewhere different (one mate of mine did all sciences and english a-levels) so i wouldn't be too worried. I would focus on your graphic work if I had had it for the interview but its quite free-for-all.
Like I said, you'll probably have a Skype interview or go through clearing but I think its just a chat on those two. I did a whole 4 hour in person interview back in the January but thats in the interview months.
Topics: hard to explain, you have a creative module, a factual module (like what advertising is, how its formed and its history), and then a lecturer specific.
I really love the course. I didn't know what I wanted to do but I'm really glad I went here. I don't really have a gripe, only tips but I'm a student mentor so if you do get in, you'll be hearing those at a fresher/mentor event the day before term starts. Good luck!