All sorted now. KPH and metric units on the digi display.
An email to BMW customer complaints got things moving, as none of the dealers seemed interested. Supplying dealer has now done the deed, and been thanked for the work. A change of staff at service department has also improved things. Calls actually get returned in a prompt manner when they are away from service desk.
Only way to carry out work is an update of the software via the BMW computer at dealers. Downside is the same process required if you want it reversed. Silly design. No matter, happy days.