It depends on when the tests arrive so people can test at home if they've had coronavirus.
If they could start testing now, we would begin to get a picture of the spread in the population.
However it looks like the tests won't arrive for another 6 weeks at least.
The delay in getting the tests out will dictate when/if schools can reopen.
Once it's clear who has had it and who hasn't, then those people who have had it, can start to get back to normal. If for instance enough people in London had had it, like 60%, then herd immunity theory could follow and London could open up again.
And potentially even if only 40% had had it, then they may open up anyway and expect another wave of sickness but know that it would come to the end 12 weeks later but allow full opening knowing that once the danger had passed for those that are vulnerable, life could carry on again mostly.
The sooner the tests arrive the sooner we can have some answers. Right now I'd say no one really knows, there's just not enough reliable data to make any predictions.