While I am not privy to the inner workings of the UK's plan, it seems to me that there are so many holes in the arguments of people defending it in this thread:
We are saving the lockdown for when we need it most
Currently, without drastic measures, the virus is spreading exponentially. Each day that you leave people interacting with each other, you are adding thousands of cases down the line in a couple of weeks, with potentially thousands of those needing hospital care. Surely it makes sense to limit the number of cases as early as physically possible, to allow for proper treatment of those in bad shape, while also having some form of capacity to treat the growing(much slower) number of new cases, which are an inevitability? Also, if the over 70s, who you claim would end up looking after the kids in a lockdown, are locked down themselves, who will be looking after the kids?
What is the point of going into lockdown when the virus has already spread far wider than the health service can handle? How will the country cope with that level of sickness, even from a mild cases perspective, where people will have to stop working and quarantine no matter the sector?
If we close everything down, who is going to look after children etc.
Some of the stats being thrown around regarding the amount of health care workers etc. that would literally have to stop working to look after their children seem wildly exaggerated. Other countries are having to deal with this scenario now, are they failing? It's a one in a life time situation, solutions will be found to these sorts of non-essential questions. The amount of companies allowing people to work from home, closing down for a number of weeks in the case of full blown lockdown will mitigate this issue considerably.
Once these other countries stop the strict isolation measures, it's back to square one
This is just such a ridiculous argument, do you think all of these countries are just going to announce that people should resume licking each other's faces 9AM Monday morning after the lockdown? Clearly, governments and businesses will be equipped with more knowledge, and better plans to cope with community spread after this period of lockdown, more will be known about the virus, and in general, people will be better equipped to deal with measures to mitigate the spread after experiencing something like this. This will lead to a lower rate of spread than before the lockdown, where half the people weren't even taking the issue seriously, and companies etc. were still scrambling to understand what was going on, and what the could do.
Some answers from those backing the UK's plan would be greatly appreciated.