I decided to add in some bushes so that the stainless bolts could be tightened and still allow the mechanism to move smoothly. I prefer to do it this way rather than rely on a nylon lock nut tweeked until it's "just right".
I turned down some stainless tubing (10mm O/D) to just thicker that the stainless plate (6mm). I then drilled a 10.5mm hole in the stainless plate to allow clearance for the bush.
The bush is a little slack in the hole, but when tightened up fully, it rotates very smoothly.
I did this for both ends of the mechanism.
I have bolted up the end of the handbrake cable using a stainless bolt. Once installed and set to the correct height, I have now bought a M8 bolt with a longer shank so that the handbrake cable end doesn't touch the threaded part of the bolt.
I mounted a rubber coated stainless p-clip on the rear brake tee-piece to help guide the handbrake cable. I will place another p-clip on the differential to assist too. The external sheath of the cable actually moves the handbrake mechanism so the route of the cable has to be kept neat and with sweeping bends to keep it all smooth.