I have made the mod - not the additional resistance, but just the diode across the existing circuit. I just jammed the dioide into the 'back side' of the male connector (titter titter) and taped it all up.
Worked beautifully! Took about 4½ minutes and cost 38p in Maplin.
My question now is - will the airbag deploy (and deploy corectly) on the passenger side if the system detects a collision or have I effectively now disabled my passenger side airbag?
Appreciate any guidance ...