Hi there, all,
I've been away from this project for some weeks, due to other priorities. This post is really to round off the thread.
We recently managed to get the table saw set up on the 'grass' and rip a 45° chamfer on one corner of a length of 3" x 1" and another on the diagonally opposite corner. I'd previously cross-cut the board to length. This length of board was to be the trim-strip or fascia to support the overhanging edge of the end steel roof-sheet. See this photo:

The first chamfer put a slope on the part of the board that would extend from under the roof-sheet, while the second was to act as a drip to throw off any rain-water running down the outer face. After applying a couple of coats of Duck's Back and letting them dry, then marking-out and drilling the screw holes, I applied a length of butyl sealing strip to the upper edge of the board. We then offered up the board and fixed it in place.
It now looks like this:

All very simple, even too trivial to mention, one might say. But, this operation was a milestone, it's the last stage of the re-roofing project.
As you can see from my thread on the ML7 Quick-Change Gear-Box, I've started to do some work IN the shed. I'm already noticing the benefit of the improved roof insulation and I anticipate that I shall be able to work in the shed more often in the extremes of winter cold and summer heat.
I just have to get used to the sound of the rain on the steel sheets.

Goodness knows what the noise of hailstones will be like!