[BLS07]

Thanks SW&GER !

I’ll try those tests too, much appreciate the advice!

Yeah, exactly. It’s odd.
Grey wire off = no headlights at dipped beam
Grey wire on = LH headlight only at dipper beam
Switch to Full-Beam = both LH & RH headlights ON.
Brake-lights = ZERO response if Headlights or Parker’s ON.
Brake-lights = FULLY responsive with NO headlights on (instrument switch all-the-way-in ie OFF)
Indicators = All four work fine ALL times in ALL above scenarios.
Reverse Lights = as per indicators, no sweat.
Interior lights = as per indicators, no sweat.

Multimeter arriving Monday, I’ll get into testing across each point with that too.
Headlight sockets / wiring in from harness / junction box / wiring into foot well that feeds the Brookhouse interim foot-dipper switch / tail lights ...although every aspect of the rear lighting works fine, when headlights OFF / instrument lighting connections/ relays in engine bay.

Puzzled..

Cheers!