Are they still sending interviews out? Wow, you did really well on bmat, what were your other stats? They might've changed the way they do it because my BMAT was lower than yours I got 5.7 5.4 3.5A and I got my interview in November/ December tkme.
Yeah I got an offer like a couple of weeks back. They get back to you around 3 days after.
Just stay relaxed, more of a chat than interview and you'll find it doesn't last long at all. Mine was around 8 minutes. I'd definitely say this is the sort of interview you can over prepare for and I'm not usually the type to say stuff like that.