Here's something to think about. The A4119 (M4-J34) into Talbot Green is covered in contra-flows and cones (started Mon 2nd August). The Monitron camera by Corner Park Garage is both a red-light and speed camera but while the work goes on the lights are switched off and covered over (the camera isn't covered though).
Now, the roadworks are a 30mph zone so it's possible the camera (which is usually set to 50) has been reset to 30mph.
These cameras don't flash (infra-red), don't use radar and don't have film. They can be reconfigured remotely too I believe. So the first you'll know is the letter on the door mat.
Andy.