In brief, start moving to the Swedish model right away. Precise timing for easing different restrictions must obviously be decided, but we should literally begin the process tomorrow. All of the evidence and scientific opinion featured on this site leads to a
very obvious way forward, which is what we should have done in the first place.
We should shield the over 65’s and other vulnerable groups, and let everyone else get on with their lives. In the UK the vulnerable people make up about 20% of the population. They suffer 90% of the deaths, and they are largely inactive economically. Locking them down therefore has a minimal effect on the economy, and a maximum effect on death rates. Then the other 80% can go about their lives infecting each other, with absolutely minimal harm, until many are immune; perhaps 55%, perhaps more, at which point herd immunity would be achieved. Then the over 65’s can be re-integrated with very little risk.