I've now given-up all hope of ever seeing either the decal sheet, or my money back. As they are the only suppliers of my chosen livery, I'll have to re-paint the car for a different livery from a different supplier.Still not replying to me.
DaveLat posted above that the decals he's had from Atalaya were sent by UPS. Mine were sent by Correos . At least, the tracking number they gave me was a Correos one.