Awfully bad manners, Georgie. Find that the best response is to smile beautifully at them, might even wave in friendly fashion. For some reason I don’t understand, this drives them even more bonkers. Did this to a bloke who pulled out from side road in front of me on major road. I had to do emergency stop. Much shaking of fists and shouting by offender. Don’t understand why, I mean I didn’t hit him or shout or anything. Friendly smile and wave so enraged him that he hit his head on window frame. Satisfyingly amusing.