Regarding the amount tested.
Italy was 23/24k tested as of a week ago (2nd-3rd of March) with 2500 cases and 79 deaths on their hands, that's a 10/11% positivity rate.
UK 9th of March 24,641 tested 319 positive (1.3%) 5 deaths .
For the low key situation UK has been in for the last two weeks UK done a decent amount of testing.
Since the lockdown Italy has tested about 25k more, up to 49k.
The situation is a lot different, Italy is a hot spot and we're not simply lagging behind a days, if we were then we'd be on around 2000 cases and 70 deaths or if you want to stretch it to a two week lag we'd have to be on around a 1000 cases and 40 odd dead.
Spain and France has some serious looking numbers, UK might follow suit soon, I'm not saying we won't be but we're not simply lagging by few days or week or two weeks. Spain and France are with around 1500 cases and 35 deaths each.