Gatso advice please

[dax_j]

Hi hopefully someone can help. I got flashed yesterday in an industrial estate (high accident spot with loads of kids about...not!) Turns out it's a 30 and I went through at 40. If they want the fixed fine to stick do they have to have a speed limit sign within a certain distance of the camera to make drivers aware of the speed limit or do I just pay up when the fine comes through the door? thanks for any advice given