I am not an epidemiologist.

But the SIR model (Susceptible, Infectious, Recovered) of infection is actually very simple to model in a quick spreadsheet.

Best fit I found was:
Ro = 3
Mortality = 1.0%, avg 18 days.
Infectious period: day 5 to day 10.
First infection: late Jan.

The good news is the Chinese appear to have got the Ro figure to below 1.
Ro = No. of people each infected person infects in a population with no immunity yet.
When Ro goes below 1 the epidemic peters out.

The bad news is our Ro appears to be 3.
If it stays that way this:

If we have an immediate lockdown TODAY and get Ro to below 1, like the Chinese have done, this:

If Johnson had acted on the 15th March (when the scientific backlash forced https://www.express.co.uk/news/uk/1255476/UK-coronavirus-U-turn-herd-immunity-Matt-Hancock-Boris-Johnson-Government him to abandon "Herd Immunity") this:

If he had done it on the 5th of March, when he was pursuing "herd immunity" and telling us
https://www.youtube.com/watch?time_continue=4&v=PdzBwotrpp4&feature=emb_logo
we should "take it on the chin"

If he had done it on 28th Feb, the day he visited a Hospital in Kettering and later boasted
https://uk.reuters.com/article/uk-health-coronavirus-britain-handshake/johnson-coronavirus-will-not-stop-me-shaking-hands-idUKKBN20Q1K2
about shaking hands with corona patients.

If he had done it on 18th Feb, when no less than President Xi of China phoned him personally
https://www.chinadailyhk.com/article/121599 
and told him EXACTLY what needed to be done.

Johnson, Cummings & Michael "had enough of experts" Gove have blood on their hands. THEY MUST NOT GET AWAY WITH IT!