It depends, do you have a seperate voice module? That is hard coded to German, so there is nothing you can do about changing that. If you have a BT-ULF which has 'mit SES' written on it you can change that to English if you want, just use the SES-jumper plug (€ 15 at you local BMW-dealer, they probably cannot find it immediately but after putting the request through at the main office they found it ). With that plug the SES of the BT-ULF is used, which can be switched between German and English depending on the settings of your language setting.

What I also did was that I bought a CD with the latest Dutch firmware, updated my nav-system and everything is now Dutch (both the menu as well as the navigation voice), only the SES is English (that does not exist in Dutch). I do not think it is possible to use English menu and Dutch nav, it is one package. Possibly you can have English menu etc and Dutch spoken instructions, but then you need to be able to do some serious coding to combine the two and make a new firmware.

I also have the German manual with all the speechcommands, if you drop me an email at c_setag [at] hotmail [dot] com I can send it to you (and if you want an image of the Dutch nav software that is probably also no problem )