Matthew,
HAve you tried a completely different approach??? How about suggesting that you meet in the offices with one of the 'trainers' or instructors - whatever they are called - and 'walk through' the HC (re cycling

) and more importantly, a copy of the salient sections of Cyclecraft? If you were to walk through some of the rationale behind Primary and Secondary vs riding in the gutter etc, it may really make a difference?
You could even offer to take him/her out on a bike and ask them to ride through pinch points amongst traffic etc? Get them to ride properly in the gutter vs Primary at junctions and especially roundabouts?
Even simply chatting through with some paper and a pen may make a massive difference????
That is the route I would go rather than emails and complaint letters at your stage - i.e. living there and seemingly getting to know them and every professional driver locally!