Well tinybill, I work with the footway gritters for red routes in central London. We are given daily emails (red, amber or green), our info comes directly from the met office. Sometimes the snow just pops up on very short notice, but generally we do get fair warning and the council always gives us the go ahead if the situation arises for gritting. Bear in mind in can cost London THOUSANDS and I mean in the hundreds of thousands to do a full gritt! The councils do the best they can with the budget they have been given.