[Dark Skies]

If you're having the same bizarre problem then try looking at the relay connections on the popup motor under the bonnet (hood). I found that slightly touching the relay operated the motor. When I was suffering poor idling the rough vibration was jiggling the connections sufficiently to cause the lights to operate and thus masked the problem. Once you've sorted any poor idling problems the headlight bug can reveal itself. I stripped the headlight motor down and pinched the female connections sufficiently to tighten them. Sorted! Thought it might be worth passing on.