Italy went into lockdown in the Lombardy region in Feb and nationwide a little later because around 6 thousand cases had been reported and a couple of hundred dead. We were lucky in the UK, we could see what was going on in China and Italy and were forewarned... but our gov still waited until 23rd March which is a fairly long time for the virus to spread.. Perhaps had the UK acted quicker and the rules & police stricter, we could've saved quite a few lives.
Had Boris acted and the numbers infected & deaths low then am pretty sure Boris would've been praised for saving so many lives - we can see what happened in France, Italy and Spain.. Had it all be contained well then perhaps the disturbance and economic cost may have been shorter because it would've been over quicker.