Thats bollocks about 'expert opinion'. They need to have evidence that you were actually speeding. Ie a speed gun or a speedo reading if they were behind you and the speedo must have been recently calirabted etc. They definately can NOT do you based on an 'expert opinion'!
You have only got a producer mate. Nothing to worry about. They record the details of your mot and insurance on the HO/RT2 form at the station when you produce. This doesn't go anywhere so no worries.
They most certianly can prosecute you if in their (ie 2 of them
) expert opinion you were speeding.. your speed does dont need to be proved as it is an absolute crime...