Hi Simon
Tax disc is held on with waterproof clear tape cut into a circle.
Kin Hate bolt on Tax disc Holders.
Rear reflector is a piece of 50 x 60mm 2mm ally sprayed black and a kink bent into it.
then eBay self adhesive reflector and some foam tape onto the back of the plate.
Local Plod don't seem to see the tiny plate if it has a reflector under it. (PROB MY IMAGINATION)