A very productive weekend. :-)
On Saturday I pushed on with the recessed ceiling and filled in the gaps at the edge of the first recessed layer. These were pieces about 26cm long to fill in the remaining areas open to the ceiling mineral wool. It is so much easier working with small pieces like this and achieving a good fit is a breeze. These layers take a long time because they are cut into strips between the joists. A lot of cuts and effort, whereas large sheets are less time consuming. I've got that to look forward to for the walls and the final ceiling covering layer. I finished off by caulking all of the joints and gaps and smoothing everyone off ready the second layer.
Second layer: This time I fixed the full length pieces at the opposite side to ensure that the joints were staggered. This went pretty well and I managed to get all but two lengths in place before the end on the day.
I continued on Sunday with the final full lengths of the second layer in the main area and filling in the 26cm gaps at the ends. All that remains with this layer is to fill the small areas in the left and right alcoves at the back and the airlock area. I am leaving a ceiling access panel in the airlock because the lighting junction box is above here. This allows access just in case. I managed to start these areas which you'll see from the photos.