Been through loads of gatso facing me and set em off never been done.
Got done by a trevello one which faces you flashed red- anyone who says though dont CLEARLY has never been done by one.
Also been on a speed awareness workshop- they only offer it you ( in Warwickshire ) if you are on the point of prosecution and they only offer it for speeders in 30 and 40mph zones- its like a let off and they know it which is why they only offer it if you haven't gone too far over the limit.
They also dont offer it if the 3 points you should of got would make it 12 on your licence the same way you cant have a fixed penalty if you have 8 or more points.
Although I'm not expert I have managed to get about 25 points on my licence in the last 8 years and have been done by speed gun, pulled over, been to court, Gatso'd and Truvello'd.