Dave Liquorice formulated the question :
All we can do is watch the hospital admissions and once they are
showing a consistent fall for a couple of weeks, lift some of the
more draconion ones and keep a close eye on the admissions. If they
start to exponentialy rise bang the restrictions back on. The tricky
bit is spotting early enough the difference between the rise that
will occur when the restrictions are lifted and a rise that means
it's starting to take off again.

The big problem with that, is the long lag between lifting restrictions
and the infections appearing.

Sensible would be system of lifting restrictions in a closely confined
area, as a test. In Italy they have isolated a village for experimental
purposes.