****EDIT****
I now see that TiRed has made a very interesting post, so everything after this edit is probably now incorrect
**** end edit ****
Aargh, I thought you had it there scotroutes. Nice try.
Something about the description didn’t look quite right though so I checked, and no, the mounting face cannot be turned 45º – it just seems to mean the clamp can be used on handlebars or seat posts.
Surprisingly it appears that the mount I need does not exist, though I’m now writing to Magicshine to ask why not.
I do have one of these:
Magicshine Tail Light Saddle bag Clip
… so I’m going to use it to bodge something up – probably using zip ties and bits of old inner tube (my go-to bodge materials, you’d be amazed what you can create)
thanks for trying everyone.