After sending another email to follow this up, I got a response - word for word the same as yours -
"Hi
Thanks for sending in these pics. The coating is designed to help prevent against the onset of any rust, however as the parts are made from cast iron, we cannot offer any product which will guarantee protection indefinitely.
I have checked the thickness readings from when you purchased - to ensure the coating was adequately applied - and they are showing as well within tolerances.
We can certainly send out some high temperature coating which you can apply to the hub section?
Please let us know how you wish to proceed.
Thanks
Claire"
And my reply -
"Hi,
Thanks for your response, I guess having some high temp paint I can apply would be useful.
I'm a little confused though, as to why this has affected only the rear discs, and not the fronts.... are the discs made from different material? I would have thought both are cast iron? Is the paint used to coat the rear discs different to that of the front?
As shown in the pictures, the fronts are exactly as I'd expect them to be, but the rears don't seem to have any coating on at all... the disc has just rusted. The coating on the front discs actually feels different, you can quite easily tell it has paint on it, but the rear discs just feel like metal. There's no silver paint, no flaking/removal of the paint/coating just metal and rust.
I know there's currently someone else on the Clio197.net forum with the same issue - they only bought rear discs, with the silver coating, and within 2 months of fitting they've rusted identically to mine. I know the paint wont last forever, but surely anything less than 12 months it isn't even worth offering the coating service on rear/solid discs if it doesn't actually work? "