@Brrrr10, yes, the HM just told us the stats without us asking. He also told us our son's marks on all papers, possibly because they were quite spiky (v g Maths and VR, not so good English). I'm sure it's fine to ask if they don't tell you.
There was a lovely current parent who welcomed us and told us loads about the school while we were waiting to see the interviewers. For the interview itself, I'd say to be ready with a few questions and to tell them about your son. It's all quite relaxed. We probably didn't say all the things we'd intended to say, but hey ho.
After talking about his 'item', our son had to do an English comprehension during his interview, due to his lower English scores - yikes, not sure how that went. But that was because his Maths/VR scores were scholarship level.
However, we were told that unless our son swore at his interviewer (! I don't think he did!!) or did something really weird (who knows?!), he'd probably get a place. Fingers crossed!
Whitgift interview tomorrow, and then I think we're all done and just have to wait for the letters in Feb...