And it was only the other day poor old Greg was receiving a ribbing for his "speed awareness", i think he's just trying to prove a point

Seriously though, that is a pisser. As far as the speedo and wheel size thing, your probably right. In the past i've used "Speedy Cables" in Islington (London). You have to remove the speedo, count the number of turns of the speedo cable for 7 revolutions of the driving road wheel, and send the speedo with that info to them, and they calibrate the speedo accordingly, apparently. I wasn't happy with the service, and subsequently, have resorted to the "Paddy" method in the past, Just without the tip-ex I thought road speed to speedo reading could be checked on a rolling road