So it seemed a good idea to make something from them. Like a bag. After fiddling about with ways of constructing a bag without having to hem too many ends, I worked out a sort of spiral, which forms a lop-sided tube; still needed to join the long sides together, and several ways of finishing the ends were considered before I chose to hem the narrow end at the bottom, and finish the top end by passing the cut threads through the weaving and braiding them on the front.
I had to cut the narrow inkle and stitch it to make the loops, though.
The bag is about 8" wide and 7" high with the top folded over. And at last I found a use for a boxwood acorn cut off a roller blind over 30 years ago - I knew it would come in handy one day!
The idea is that the sash will be simply knotted round me, and the bag is big enough for the essentials, while the clip can take keys if needed. The sash could also be knotted shorter, to make it a shoulder-bag or an across-the-body bag. Will the theory work out in practice?