I do not speak French, so I know little about the correct pronounciation of these words. What I can say, is that his "made up Polish" in Warszawa was not a very good impression. And likewise, people have remarked on poor pronounciation in songs such as "Helden". My Indonesian friend laughed when she heard the Indonesian version of "Amlapura", although she considers his attempt at "Don't Let Me Down" much better.
Bowie does not have a good knowledge of French, so it would not surprise me if his pronounciation is not accurate. In 1997, he spoke English on French television and the interviewer translated for him.
The Music is Outside