This is a long shot but someone might remember it from a while ago.
There was an English tv series (maybe one two or three episodes). It was set in France and involved the kidnapping of, l think, a small boy.
The family had to find him (naturally). I seem to recall them driving around in a Citroen but it showed lots of shots of the French countryside/roads etc.
Sorry it's so vague.
'France' and 'Kidnap' made me think of 'Red Fox' too (John Hurt, Jane Birkin mini-series 1991). But the kidnap victim was Birkin's husband, Brian Cox. No family in a citroen, either.