This was not the way it was supposed to be.
The project is complete, but it is more of a hack than I wanted it to be.
First the success: There's light!
Now the ugly:
The light is no longer powered by a sleek, single-purpose box, mounted on a bespoke bracket, but a wall-wart cable-tied in place.
The change was not of my choice. This morning I went to do the final connections. It all went well, and just as I was to demonstrate the final product, a final flick of the switch failed to produce light. Upon inspection it proved that the fuse and blown and the transformer had gone open-circuit.
(I guess the fact that the fuse failed to protect the transformer is just another indication of the poor design of the UltraTec products.)
Here's another view of the light in working order:
And here's the dinky little switch that powers the whole thing:
The client made the new cover for the light, out of polycarbonate sheet. In case it needs to be replaced there's an extra, and also templates for making more, should the need arise.