Dd also has had interviews at Channing and Highgate. From the numbers of people at both I'd say they were interviewing approximately 200. So with only 40 places available I'd say we're still talking v. long odds! I'm being hopeful rather than confident.
The fact that so many people apply to so many schools means that a large amount of applicants are not relevant. If you have applied to multiple schools you can't go to all of them. If every applicant has applied to say 3 schools then (assuming the 1st preferences are distributed evenly) you have a good chance.
66 real applicants for 40 places.
Of course the real outcome will not be known until the offers are rejected by those who were offered but do not want to take up a place. So... it is quite possible that being wait listed might result in a place.
A long lingering torture...
That's my interpretation anyway.