Who knows, and that is a large part of the problem, seemingly no one does.
One of my son in laws works in London. He relies on shared accommodation. His head office, in Los Angeles, now insists that the US staff work from home, but not so their UK staff! If he were to self isolate in London he would only have a room to go to for three nights a week. I am sure that there are many thousands of others in the same or a similar situation. Inevitably he would want to come home, who can blame him.