I think all that calibration certificate malarky is just delaying the inevitable and coming across like a wanger. Best to just own up to the deed and take it like a man. I understand doing it if your on 9 points already and plan to take it to court, but otherwise you will save your dignity and time by just taking it.
I was recently pulled for undertaking, a manouvere I wasn't fully aware of being illegal. I always thought undertaking was passing a car on the inside and then pulling back into the outside lane, the opposite of an overtake. But I was informed that simply driving faster and passing the car in that wrong lane was an undertake, regardless of wither I pull in front of him or stay where I am.
I owned up to it and agree'd completely with his version of the events and apologised for it, he was almost taken back and informed me that it was a stupid thing to do for 6 points, and that if I wanted to drive my lovely car fast, do it in the country side, not the city. He then kindly told me to get on my way, to which I was very appreciative. I put that all down to being honest and apologetic. Sometimes it works, sometimes it doesn't. But the majority of the time, being an arrogant wanger will just get you prosecuted regardless.