So here we are at the end of the third week and, so far, everything is going to plan. This morning's machine was the concrete mixer:
and by the end of the morning the hollow was filled. The hardcore, plastic, insulation, steel and concrete make a substantial base for the rest of the house.
The concrete should be set by the end of the weekend but it will be interesting to see if anyone/anything visits the site and makes their mark for posterity like this little dog 2,000 years ago (I bet the tile maker was delighted).