And lo and behold a possible solution arises! With thanks to SJS cycles
https://www.sjscycles.co.uk
Because the hub came off a bike with seat stay IS mounts, it has a
speed/monkey bone plate. However...in an attempt at options I measured
various distances, and as far as I can work out, axle center to rack
mount is 35mm. A phone call to SJS and they measured various dimensions
on the Axle plate TS-8233, it turns out, you guessed it, center to one
of the holes is 35mm, the hole diameter being 10mm giving a bit of room.
So, replace the 8228 plate with an 8223, and if all matches, a bit of
pipe to fill the M6 rack bolt out to 10mm, if not, Bodgit & Scarper, cos
at least it's out of sight! [1]
Now, if only I could find the 8223 that came off the hub some 5 years ago...
[1] In fact the outside diameter of a 'normal' M6 nut seems to be 9mm
which is good enough for me.