I can see where they are coming from with easing Christmas lockdown rules, and at least all 4 countries have agreed to the exact same rules. Personally we won't be meeting up with family like we usually do, with one possible exception. My wife's sister lives alone and her oldest son and family live close by but every other year they drive to Mull at Christmas to stay with his wife's family. This is the year they would normally be in Mull, and her other son and wife live in California so won't be visiting like they usually do.
We don't intend to leave her alone over Christmas week and will drive up to visit her if in fact she would otherwise be alone. She has been super cautious throughout the pandemic, having had open heart surgery in February, just one year after becoming a widow.