Indeed, the Japan units won't work for anyone outside of Japan

Japan navs fitted to BMWs are made by Alpine and use a Japanese-specific map disc for the Japanese market. Totally different to the VDO nav.

As well as that, the menus are in Japanese, and extra features like the VICS system and Toll Collector system are integrated

The Japanese nav systems out of Japanese BMWs and Rovers and Minis are simply junk outside of Japan.
The only useful thing you can do with it is throw it away.