I think that you will find that the ???? switch is for the instrument panel illumination. These lights can only be switched on when the 'lights' switch is on. Your 'lights' switch initially only turns the side-lights on, the headlights are switched on by the column switch, which should also control whether you have your head-lights on 'low' or 'high' beam and, when only the side-lights are on, enables you to 'flash' your head-lamps (by pulling the switch towards you). This is how the lights work on a RHD car, I can see no logical reason as to why they would be any different on a LHD car.