I follow some Acute Medicine Consultants on social media - they report that between a third and two thirds of the acute admissions in their hospitals are Covid or probable Covid. Sharing with two other households over xmas? No thanks.
As Chris Whitty said: "Would I encourage someone to hug and kiss their elderly relatives? No I would not...If you want them to survive to be hugged again."
I would go further - don't even share space with them inside - spend time on zoom, or socially distance outside.
The Government must have worked out how many illnesses/admissions/deaths the three household/five day rule will cause - but they are not telling us.