No. 1 is to be better prepared. Around December/Jan governments were observing what was going on, and planning. in Feburary, our PM skipped 5 Cobra meetings!! Five! The Times headline is the UK Sleepwalking into Disaster.
https://www.thetimes.co.uk/article/...n-britain-sleepwalked-into-disaster-hq3b9tlgh
If you are to lockdown - make sure it works!! If you are going to close the nation, do it well! Make sure it is for a reason, not just going through the motions. And get testing and tracking in place to maintain things when you open up. Ensure visitors are screened. Secure the nation. The faster and more stringent the lockdown the quicker the UK recovers. In theory, a two week draconian lockdown should get things under control.
Hindsight is a wonderful thing, but even at the time, people were calling for the right things - faster action, better testing etc. Our government were the least prepared it seems.