A week later the wall and ceiling sections of the basement were installed. Each section was craned in and held in place with metal supports. The external walls were hollow with rebar holding the two concrete sections apart. The windows were already fitted. The internal walls were then placed inside before the sections of roof were laid on the inner part of the external walls and some extra supports they had erected. All that was done in about five hours.
The next day they added more rebar to the roof and particularly the ceiling-wall joints. The hollow walls were then filled with concrete which then spilled over to fill the ceiling. The weather was good and there was plenty of time for it to set.
The weather didn't hold though. Just five days later there was an amazing thunderstorm that sat directly over the site for hours. Houses were flooded and buildings were struck. I went to see the site the next day and we pretty horrified to find nearly a metre of water in the excavation surrounding the basement. I couldn't get into the basement but when I peered through the window it appeared to be pretty much dry. The hole for the stairs was open so I wasn't surprised it was a bit wet. The fact that it was otherwise fine inside suggests that it is indeed nicely water tight. And the sight of the water around the basement confirmed my decision to go for the full water-tight design even though it was very expensive.
The water has pretty much drained away now. The basement was inspected by the house company (it passed) and plans and a date for the construction of the house are now being confirmed. I even have dates for the delivery of the staircase. Before that the basement needs to be finished with light-wells, insulation, drainage and the earth needs to be put back. Busy but exciting times!