Hertz nav in europe is normally the car mfr's nav system ordered by Hertz. Some systems do NOT allow English to be loaded without English CD/DVD (which Hertz France as an example won't recieve with the car). There is NO neverlost(tm) in Europe as that system has no datasets being compiled for Europe.
So be forewarned. The BMW's and Mercedes Benz's rented by Hertz with Nav *DO* allow the nav system to be switched to English without needed new media. So do some other models.
To be honest if you have a basic French/English dictionary you could figure it out anyway....
PS: Try looking for the nav disc on one of the peer to peer file sharing sites; they are quite often up there and if on a hotel high speed connection - they aren't always that large... I've done this twice for a Toyota nav system...