From what the political reporters are tweeting, it looks like while a lockdown of sorts *is* coming, it won't be until later next week. Looked at purely in cold logical terms, it's hard to see a justification for allowing mass mixing of families across the over the next week and a half while the growth in infections is increasing, only to lock down when people have travelled back to their own home locations & potentially mixed with different groups over a matter of days (work colleagues* up to the 24th, Family from various parts of the country on the 25th/26th, friends & neighbours after that). It's a recipe for spreading the variant far & wide.
*excluding work meetings with wine, cheese & pizzas in the garden where your wife & young baby are in attendance, of course...