I am in Japan--the schools have been closed for a week. It's hell but the evidence shows that it will reduce deaths a lot by greatly slowing the spread of the virus.
Afterschool childcare facilities have remained open and have started all-day programs, but these facilities are much smaller than schools. And of course, some kids are not going to the childcare centers at all because they have a parent who does not work, WFH or has been told by their company to WFH for this period--if you are in these groups you are told to keep the kids at home.
So instead of having all children spending their days in a few large groups, you have a rather smaller group of children divided up into a much larger number of smallish groups. Is it a perfect system in terms of disease prevention? Hardly. But at the macro level, it reduces the number of vectors per child a LOT, meaning that the virus spreads more slowly, buying us time and spreading out the rush on the hospitals.
Of course kids do go outside, hang out and go to parks, play on the streets. But again, far few vectors per child.
This will be your reality in the UK before long, so unfortunately you will all have to get used to it.
It does suck though. I am trying to work from home with two kids knocking around and am literally crossing off the days till school (hopefully) starts.