We can however do some rough What-if's based on such attitude / inaction.
The population of the lockdown area in Hubei is c60 millions, not that different to the population in UK.
With major intervention, they "achieved" the result of c100,000 infected, c3000 dead. 100,000 is only 0.17% of 60 millions.
In UK, the
worst case scenario has been set at 80% infected by the government. Let's say that is pessimistic, and call it 50% with little intervention. If we simply scale it based on the Hubei statistics, that translates to c900,000 dead.
Except that in Hubei, they managed to draft in 40,000 healthcare professionals from elsewhere in the country to help the 100,000. With 50% of 60 millions infected in UK, those requiring intensive care would number millions - meaning the vast majority of them would get ZERO medical attention - medics get infected, e.g. from family members, too. So, 900,000 dead would likely be a VERY optimistic number in such a scenario.
That is the kind of place where complacency can get us. Just saying.