Ep 16 is scheduled for live broadcast on Sky Witness at 10pm on Wednesday evening.
So i would expect this episode 16 to be added to on Demand sometime after 10pm on Wednesday.
Ep 17 will follow a week on Wednesday at the same sort of time.
It’s not started in the US yet.
Depends on the rights Sky has with the show. Could be kept for Disney+ like 9-1-1 Lone Star season 3.