When you say clocked do you mean just to keep them below the stipulated PCP annual limit or more sinister ?
More sinister. Search the Mercedes forums. People are buying clocking devices to take advantage of the ridiculously low mileage stipulations.
That is bad news - in my innocence I assumed with the electronic odometers that they would be pretty secure.
Is the only real cross check against the historic recorded MOT mileage then ?