You asked “Where did [the early Christmas Day service] take place?”, having suggested it must have been before the tv crews arrived at 4am, and linking to the parish website. I presume, implying that it hadn’t happened. I suspected your question was disingenuous, but nonetheless showed you a time stamped text explaining where and when the service took place.
Going back to the question of the thread, I note with wry amusement that today a poster on twitter (with sussex squad in their username, there’s a surprise) has posted footage of Kate taken on Christmas Day 2013 - when she wore the same hat as she wore to church this year. In the footage Kate was saying that George was with a nanny. The user has posted this as “confirmation” directly from Kate that she and William are separated and their children are being cared for by nannies.
Unfortunately for the poster, while the hat is the same, Kate wore different earrings in 2013, and so it can easily be identified as footage from 11 years ago. Unsurprisingly therefore, it was then 5-month old George who was back home with a nanny while his parents were at church.
It hasn’t stopped the credulous Twitter squad lapping it up, but if 11-year old footage of Kate can be used now on the basis it was taken last week, without people noticing that she looks obviously older, she clearly wasn’t looking too bad on Christmas Day…