Yves, I think you may find that NavCoder at http://www.navcoder.com/ is the answer for you. It allows you to add/replace languages directly into your car's system via the iBus, and they say it works with Mk2, Mk3 and Mk4 navigation systems.
Anyone here have experience of using NavCoder ?
I've just got an Italian Mk4 DVD/SatNav from eBay which only displays Italian (default), French or German. No English, damn, so I may have to go that way too (need to get a special Resler cable as well to tap into the vehicle's iBus, I see),
... unless you want to upgrade to a Mk4 DVD Navigation which can display and talk French, that is, Yves! Euro 100 + postage. V32 S/W installed. Free 2005 maps DVD (does read 2019 Maps DVD I notice).
French Italian or German lessons could be another alternative for me, I suppose.