Hi Jack.
The "Handbook of Rules and Guidance for the National Safety Camera Programme for England and Wales for 2006/07" states:
DfT wrote:
Rule 5: Site visibility
Dependant upon the enforcement method used, speed camera housings, or the camera operator or the mobile vehicle must be visible from the driver’s viewpoint at the following minimum visibility distances:
• 60 metres where the speed limit is 40 mph or less
• 100 metres at all other speed limits.
For mobile speed camera sites, although the camera technology may allow, partnerships are not permitted to net off from offences detected outside the approved site.
Hence you are correct; however, there is also a clear disclaimer:
DfT wrote:
Compliance with these rules has no bearing on the enforcement of offences detected by the use of safety cameras. Non-compliance with these rules and guidelines by a partnership, or representative of a partnership, does not provide any mitigation of, or defence for, an alleged offence committed under current UK law.
Hence you are stuffed anyway.
It might be worth your while writing directly to the partnership bringing to their attention that they will not be able to net off (assuming they can anyway) from that site (given your claim) should you wish to take it further to someone like your MP !!!