I would possibly agree, but seeing he's going to FRANCE I wouldn't want to know the data cost
Its not too bad. When I went abroad I just buy a "data pack" and find that the sat nav doesnt use much data at all. But, if the OP is worried about that, id definitely go for an off-line sat nav app. I use iGo on mine for off-line use and that works really well.
Scuse my ignorance, I am not an expert on this, but how does an offline navigation system know where you are if it is not using GPS or similar?