All measures, including those in China and Italy are reactive not proven.
Whether putting China on lockdown will only become apparent within the next few weeks now that restrictions have been relaxed. It is in fact estimated that China will have another spike in infections and that lockdown will be considered to have been done too soon.
The infection rate in Italy is fast increasing, so lockdown is clearly not having a great effect there.
If you lockdown the UK too early people will develop fatigue and will be less likely to comply when it really becomes necessary.
The testing protocols is the same as with other viruses. It was the same with Swine flu - if you had symptoms then you would be assumed to have swine flu.
And people talking about this being just a hit to the economy have no idea. There will be hundreds of thousands of job losses if we obliterate the economy over this. Nurseries, childminders etc will go out of business meaning many working parents will have to give up long term to stay at home with their DC. Many NHS workers will have children so they will have to take time out to look after those as workplace nurseries/childcare facilities will also close.
People will end up in serious debt, mental health issues will get worse, and there will be deaths, because of suicide, because of the impact of poverty etc etc.
Let’s not play down the impact on the economy