Saturday before last (April 15th) I finally got the last sheet up on the south roof.
After waiting ages for two consecutive reasonable day's weather I got this sheet up in one day. Everything went very smoothly but it still took me most of 6 hours to do it so I feel my caution not to be too pressed for time was justified.
Next jobs for the roof are painting the gable ends, adding the verges, adding the capping along the ridge, painting a few dings to blend in better, covering a few places where screw holes went wrong and adding the plastic caps on the screw heads.