2004 Y61 Navi X6 miles / km display Help!!

Hi Folks,
2004 Y61 with X6 navigation.

Does anyone know how to change the Sat Nav to display distance in miles?
The Nav is displaying distance in Kilometres and it's driving me absolutely mad!!!

There is NO option on the language menu to select English with different units - the only options are English and French.
I can't find an option to change between miles and km in any of the menus.
I'm guessing that there's a hidden menu or some magic button pressing sequence to change it.

I'm in England, we do distance in miles over here, not that modern km stuff!

Cheers.