It was on at 9pm. Big Brother has nothing to do with it.
It is very very odd behaviour, even for Five, especially as they've been so supportive of the various Law & Orders in the past. I was really enjoying the addition of Jeff Goldblum to the cast too! (horrible new theme tune though)
At the end of the 4th episode, the announcer said it'd be back next year.
I guess Paul Merton's travel show was more important...