If you want to fight it this is what you need to request from them because you are adement you have not been speeding because you recall this day you remember the incident (probably not the best word) you were doing exactly 30 having and were fully aware of the van or something like that

1. Full service history of camera
2. When the camera was brought on line
3. how long since the camera had a service/calibration
4. the qualifications of the opperator
5. was the van parked in a DESIGNATED police layby

also clarify the 10% plus 2 rule

hope this helps

Jay