[Jason.]

If the summer series was in January, it wouldn't work.
People usually get time off in the summer, so it's easier to be a housemate.
Plus, wouldn't that mean housemates go into hiding at Christmas.

It just wouldn't work.

I think all the summer CBB's, with the exception of CBB8 would've rated much higher if they were aired in January.

CBB10 (SUMMER) - 2.2M
CBB12 (SUMMER) - 2.3M
CBB14 (SUMMER) - 2.1M

I think if they aired in January, they would've probably averaged:

CBB10 (WINTER) - 2.9M
CBB12 (WINTER) - 2.8M
CBB14 (WINTER) - 2.9/3.0M (Due to the success of CBB13, and the decent first week)