i wasn't able to attend mine (i live outside the uk), but basically they collect all the portfolios and check them. there might be a short interview afterwards, but only for those regarding whose portfolio they have questions. so it doesn't mean anything if you have an interview or not.
i applied for architecture btw, and i sent my portfolio online
I attended a portfolio review for architecture last week. They interviewed everyone. I would guess there were about 30 people in the group. They called us in individually, by name. We went in with our portfolios and went through them with the interviewers. There were 2 interviewers. They asked me questions about my portfolio and my choice of studies and I had the opportunity to ask questions too. Also had a tour of the facilities, which are fabulous. No one spent more than 10-15 minutes in the interview, as far as I could tell.