Well, maybe not quite as authoritative as I thought
As I understand it, the following is more accurate:
Big Brother's Best Bits is a series of 6 x 60 min (not 90 min) programmes on 5*. They will air around 9:00 pm (exactly one hour before that Saturday's episode of CBB airs on C5 around 10 pm, First programme transmits Saturday 29th August at 21:30 (not 21:00) before CBB starts at 22:30. The programmes will air over 5 (not 6) weeks finishing with a double episode on Sat 26th Sept.