Im sorry to hear about this, light flashers need to start getting punished.
Ive had it with folk flashing lights all the time, does my nut right in, i wish people would just drive and get on with driving, all this fart arsin about flashing lights, then flashing them again as they didnt see you, (or chose to ignore you!), then shaking their heads.
apologies to any lorry drivers also but i really dont need you flashing me back in after ive passed you in a skoda fabia towing a motorbike trailer, im quite sure i can handle that one thanks, your wasting my indicator bulbs by having to join in the flashy light brigade to thank you!
the amount of times im stuck behind some eedgit on the main road who's flashing people out of a junction or crossroad before he turns off, eh mate hang on a minute we're on the main road, not them, get a frickin move on, causes more congestion in the end with people flying off in all sorts of directions instead of just following the highway code.
The one time i dont mind light flashing is to warn each other when mr speedy van man is out on the road with his camera but strangely less people seem to be up for that one because it genuinely is useful!.