I totally sympathise with you all we get exactly the same down here although I have never confronted one of them they never acknowledge your courtesy unlike all the horse riders, and there are rather a lot of them up on Dartmoor which I love to see together with the other wildlife.
This is a recent trend down here that really took off when they decided to run a leg of it across Dartmoor National Park, I may be missing something here but how this was part of the Tour De France fails me quite frankly. Ever since then it seems anyone with a pulse is on a bike on our narrow roads trying their level best to become a statistic.
Wishing you all many happy miles of bike free motoring.