As an update, I managed to go into the Hermes store and try the orans on for size and I am very very glad I did. I got the gold (tan) in Size 39 and it fits perfectly.OHMYGOD! Thank you this was sooooo helpful. My feet measures 24.5 cm but I have super wide feet. So I think I might be better off with a 39 or 39.5 i think in the Orans!
For reference, I'm a size 40 in the Amina Muaddi Begum Slingbacks and a Size 39 in the Dior J'adior slingbacks and a size 40 in the Gucci Rhyton Sneakers (although I could likely get away with a 39.5 in the Rhytons). I tend to have wide feet