i was playing with INPA, and in the nav module it offered a choice of languages to be programmed when the OE firmware disk is inserted... i used to have US, ES and GB, somehow i ended up with GB, FR and ES... even the bluetooth unit changed it voice recognition responses, like it used to say "DIALING", when a number was dialed off the voice command, and now it says "THE NUMBER IS BEING DIALED" with a distinct british accent...

check the INPA and you also should have the original firmware disk, there are like couple dozen language files there...