Sorry to hear about your encounter with the friendly cops, but if I were you I would not have done what you did. Cops would not mind if you did 120 clicks on the highway, but if someone was slowing down because he or she saw the cops, you should not have flashed him.
The speed limit after all is 100 and if the cops felt that you were not concerned about their presence and not showing some respect, they would nail you.
There is an angle and height for both high and low beams, which denotes the adjustment specifications to meet the requirements for all cars licensed to drive in North America. You may find it on the MOT website. BMW would have had the lights calibrated to meeet those specifications, but being your car is almost 10 years old, it will be duifficult to prove that no one touched your lights since.
IMO, that would be a tough case to fight, but never the less good luck and I wish you all the best.
SPEED AND POWER IS NOTHING WITHOUT CONTROL,
THANK HITLER, BMW HAS ALL THREE