I've been told that Rhodium is the most hardwearing, and most light
reflective
of the
platinum metals, when used in plating, but I doubt many jewellers use/can use
this
method.

To tell you the truth I've never plated with platinum or heard of it being
done. I assume you can, but I'm not sure why you'd want to, with Rhodium being
so easy to use and available. Most of us can/do use Rhodium when we plate. A
fair amount of Sterling comes pre-plated with Rhodium to prevent (short term)
tarnishing. If you are trying to get sterling plated you may have your work cut
out for you because of contamination issues with the bath and cost. Why are you
asking the question?