I can help ypu re-code it.
If the Mk4 is a BMW nav drive, you may need to re-code it in a BMW, as it detects vehicle type and loads the software according to vehicle type.

So I can point you to how to load BMW software onto the unit, and how to re-code it to colour operation when in a BMW.

I am not sure what will happen in a Rover!

To recode it, you will need an ibus interface and a special version of my NavCoder software