Found this article on the BBC website explaining how gritting works!
http://news.bbc.co.uk/1/hi/magazine/8420755.stm
According to this - if the road surface is dry when the grit goes down, the grit is far less effective because it needs some moisute to turn the 'grit/salt' in to a brine. Also, on a dry surface, most of it gets blown away by cars passing over it.
So, in fairness to the council, they may well have gritted in good time but the surface was bone dry before the snow started. It started to 'work' when the snow actually came but it took a bit of time to kick in. That's my science project finished for today.