Garage Marchasseau Citroens
What a place! Found it quite by chance out in the countryside, more info on their website here: www.garage-marchesseau.fr/historique.php
I have loads more photos of the individual cars (more than those above and in the next photo), which will have to wait until the end. In the meantime, the CX Prestige says it was sold but it's still listed on their website for 19,500 euros.