well Sunday was spent looking at the light PCB
there is an issue which is still preventing it to illuminate, it will need further investigation and not currently having the time during the week and needing to have a fully functioning light array on the back of the car i took the plunge and bought another light.
It's in reasonable condition, but at least
a/ it works fully
b/ it doesn't look like it's melted internally in the reverse lens area
viewed from certain angles the plastic outer lens has some internal fracturing, so at a point in the future on a far drier day than currently i'll remove the outer lens from the original light and swap them over.....
but at least i have working lights again....
interestingly, with the defunct lamp unit plugged in it registered a fault on the warning system on the dash, without it plugged in, absolute nothing..... i found that strange