France speed limits

I've done quick search on here and can't see this topic, but apologies if it's been fully covered.

The Club's 2019 Touring France book states that the speed limit on France's single carriageway roads is 90 kph. This is NOT the case, although some exceptions are signed and seems to be the result of local decisions approved by central government.

I was intrigued my SatNav is insisting the limit was 80 in such cases - it's correct!

Having been here for a few days now, I must say these limits and the proliferation of speed cameras and checks seem to have transformed French driving standards, which has to be a good thing, despite the predictable outrage from some quarters. Have yet to experience the previous Russian roulette overtaking manoeuvres, although I don't want to speak too soon.

Interested in others' experiences.