Although the floorboards are still to be laid upstairs, it is possible to get around on planks (as long as you are very careful).
From upstairs, it is much easier to see the roof detail in the king post trusses. The oak is pretty much as we found it. It has been lightly sandblasted to clean it up and a number of the purlins and one of the tie beams had to be replaced. But other than that (!), it is in good shape.
Once the insulation is installed between the rafters, then these will disappear from sight. However, you will still be able to see the truss and the purlins.
This is a drawing here showing the makeup of a king post truss as well as an interactive 3D image (courtesy of Microsoft Photosynth) here.
Inside number 9. You can see the King post truss and the tenon joints (with pegs) that join the purlins to the principal rafters.
Another view of the roof truss in number 9.