There's one that they hide (sorry place) around the bend on a wide road that doesn't need to be 30mpm, so you don't see it till it's too late. Anyone noticed how many average speed cameras they've now got, and in areas where the speed limit seems inordinately low. Now they might argue that evidence that shows an increase in accidents when drivers see the camera and brake sharply, then justifies the average speed system, but being a cynic, I still think there's a lot of revenue gain going on.
I'm in favour of average speed cameras, providing that the speed limit they "police" is reasonable for the road and conditions. At least they curtail the habits of (those who I consider to be) the real "dangerous" drivers; those who drive at frankly moronic speeds between cameras, slam on the anchors as they go through, then blast away again (I've even seen marked police cars to this, so very much doubt they were trying to respond to a call).