From a 2008 copy of the Miam Miam Dodo, it seems like there are ATMs in Le-Puy-en-Velay, Saugues, Saint-Alban-sur-Ligmanole, Aumont-Aubrac, Saint-Chély d'Aubrac, Saint-Côme-d'Olt, Espalion, Estaing, Conques, Figeac, Cajarc, Limogne en-Quercy, Cahors. So it is usually not a problem to find one.
I didn't come across a gîte that took any kind of bankcard, and I think that most take only cash.
Margaret