I am currently in Beijing, and booked on the last flight out to HKG on Friday (KA975 20:30 – 00:10+1).
Would be extremely grateful if someone can tell me what the availability is like on earlier flights, to assess my chances of same day standby.

I should be ok with any of the following, PEK-HKG in Y on Friday, April 21:
CX391 13:30 – 17:20
CX331 16:35 – 20:25
KA993 18:30 – 22:10
KA903 19:30 – 23:05