Update. GOT the S-O-B!!
Inside the rear lamp housing, there was corrosion between the brass insert and the housing itself. Removed the insert (you need to be careful doing this to avoid damaging it) cleaned the rust out, re-assembled it, sorted!
Except ..........
I still only have one stop lamp, driver's side. When left turn signal is on, though, right stop lamp lights up OK, without feeding through to the licence plate lamp or others. Ignition does not have to be on for this to happen.
Any ideas on this one? :confused:
