How important to ITV (and for that matter other commercial stations) is Christmas week itself?
I'd imagine Q4 is the biggest revenue quarter, but I'm not sure the January sales have as much consumer pull as they did, and holiday advertising - which used to saturate the screen in late December and January - is more spread out, I think.
I remember someone saying up to December 23rd is the best time for ITV. December 24th until January 1st are the worst, which is why ITV never bothered to place big shows in their Christmas schedules, as the advertisers were not going to flock to their output.
ITV try to "do" Christmas on the least amount of money they can, so they can be seen to be festive and spend as little on it as possible, as the ad revenue post Christmas is appalling.
Just look at their recent festive line up, really dreadful.