Les, what exactly are you wishing to change? Obviously the KMH and MPH are physically printed on. The odometer however can be changed as can the multi-function display if fitted.

IIRC you change the control unit coding so that the second digit is a 4 which sets things to mph,mpg, miles etc etc

I dont have access to a Solus but on the Verus you get the option for advanced access to VAG, merc and some others. In these advanced modes you can change coding and work more like the dealer tool.

Matt