There are LOADS of little devices that tell you where fixed cameras are and likely mobile spots as I believe the local councils or authorities must register sites they intend to use mobile cameras, could be wrong there?
I have a setup on my Pioneer HU that warns me of speed cams visually on the map screen and audibly if I happen to be going more than the cameras limit, ideal as I don't like devices that beep all the time even if you are inside the limit.
It doesn't matter if you know the area or not it is your own fault if you get caught unfortunately...
There is a great gatso on the A2 near me, it is on a blind bend just after an underpass and if you did not know it was there you would be caught everytime, likewise one on Gravel Hill in Bexleyheath, it is at the bottom of a real incline so you have to sit on your brakes just to get past it... but no point bitching about them is there?
My missus got caught in Bromley and went on the awareness course and although she said the guy running it was a pompous self righteous prick, he did have a point when he said that speed limits are just that, a LIMIT not a target