I think its the roads too Nige. You tend to get a good fresh granite chip used up on the moors, and not very many big trucks to polish them
Works havoc with tyre wear, and leathers too if you have an off
We mostly get the 'nice' modern heavily-rolled-to-make-them-quiet roads down here now. They have feck-all grip compared to old-fashioned road surfaces, so much so that they are now putting up signs that say 'danger - slippery surface' after laying fresh tarmac