Ade,

I doubt that they are "video" camera vans, after all, how would a video show the speed of your car?

More likely to be a camera van with lazer speed detection equipment. These vans provide high quality "still images" with your speed, reg plate and other revelant info displayed on the picture.

A lazer detector would help you, it must be one with loud audible warning - e.g Valentine 1.........BUT it's often too late and the image and speed information is "captured" before you have a chance to slow down enough.