I worked it all out – I know exactly how I’m going to proceed with the detailed work. You’ll see me doing serious thinking in this timelapse (these videos cover the full day of work):
I’ve drawn up the main arch over the left side room, added more detail to the lower collar of the pillar head, added the arch join detail, worked out the scale of the moorish design and drawn up the pattern for it on the pillar head. Then I traced it all onto tracing paper and set up a large piece of board to take to site to transfer the vanishing pint lines back to the infill panel.
Here’s what my thinking desk looked like today:
Here are my workings for the scale and size of the repeat pattern:
I’ve transferred it all to the infill panel on the first pillar head, and traced it ready to take to site for measuring the perspective lines and bring them back: