Again, I disagree. My (unscientific, unsupported) experience is that supermarket car parks are becoming more like streets, rather than vice-versa, with kids in hatchback and twunts in 4x4s expecting everyone to get out of their way, able-bodied people parking in disabled bays, and over-revving and heavy braking now the norm. In any event, a supermarket visit is quite clearly bounded in space and time, and therefore the change in behaviour necessary is limited. Your average Really Important And Stressed Driver is liable to find car-park style driving too much on a limitless, unbounded basis.
Again, I'd love to be proved wrong, I just think that UK society is too fragmented, too selfish and too individualistic for this to work here. In other, kinder, more homogeneous and polite societies, yes, here, no.