for my unsw, i wore trousers, and a proper button up, collared shirt. I dunno if i got in but that's what i was wearing and thats most likely what i'll wear for my other 3 interviews.
I'm actually quite comfortable in shirt and tie during hot weather, but that's just me. I don't think I wore a tie to any of my interviews, simply because I didn't think it was so much about looking like I wanted a job so much as looking natural. Sure I'm in my element wearing a tie, but it's a lot easier to look "comfortable" when you're wearing what you wear every day.
I wore a long sleeve collared shirt and black pants, same as any other cold afternoon.
PLEASE wear something decent. When I had my interviews (not med, but OT), there were people turning up in havi's, miniskirts and boobtubes :s So much for projecting a professional image. It wasn't even THAT hot!! Needless to say, they're not in the course.