Thanks to you and Jo Zebedee for the information on all this. Very interesting and important.It's also my understanding that the first week after Christmas is the one to go for. Doesn't mean that Christmas Eve won't be good though. I suppose the hope is that people are relaxed and have maybe had a few and are feeling indulgent, both towards selves and others over the holidays. And yes, new devices and a few quid in people's digital pockets.
I originally aimed for an early December promotion (because I'm clueless) but in the nick of time I noticed that I had set the kdp discount for the UK market instead of US (did I mention I'm clueless?) so had to scramble to reschedule both the kdp countdown and the promo companies I'm using. That's when one of them volunteered the information (very kindly—I hadn't asked) that in their experience the first, second and third weeks after Christmas are the first, second and third best of the year for promotions, in that order.
BTW, if it is a competion for being clueless, think I'll still be the winner