I don't see how it could be contained, if there's about to be a huge spread, which I'm not convinced there is. I'm in London and it's very busy at the moment, with lots of tourists.
In the last few days I've had face to face conversations with people who've travelled from Greece, Italy, US, Canada, New Zealand, Thailand and France. I've been on trains, tubes and buses, in busy pubs and restaurants and to the theatre. I must have come into contact with thousands of people. I'm not sick, but I don't know if any of those people are carrying the virus.
I don't know how it would be possible to contain it. People need to carry on living their daily lives. The whole country can't stay at home.