Johnson didnt actually say Monday, he said this week. The new guidelines for companies arent even published yet and there is supposed to be various hideous detail out during the week.
"And the first step is a change of emphasis that we hope that people will act on this week."
Its psychological stuff, trying to evolve the sense of what is the next new normal, and trying to ramp up various pressures on certain workers to return to work. In reality I'm sure that they know its going to be a long process. Psychological stuff they need to indulge in because neither they or the virus are in sole control of the timetable. The attitude of the masses towards the pandemic, risks to themselves or others, and a bunch of other stuff will also dictate the reality of how lockdown relaxes, at what pace, and what the new normals are along the way. I dont want opposition figures, unions etc to deliver criticisms that contain implicit acceptance of certain aspects of the governments position and message, and I feel a bit like thats what they've done by going for a 'he's only given people 12 hours notice' criticism this evening. I'd have been happier if they just said Monday was absurd and acted like even Johnson couldnt possibly have meant that! Keep the R below 1 and the Ridicule above 1.