I did a bit of reading after my last post and found a French site where it states that "The Smooth-Faced variety of Pyrenean Shepherd is fully interbred with the Rough-Faced variety. Pups of both varieties occur in the same litters." It's the Patricia Princehouse link for more history...
Also, I can find the KC breed standard for one described as 'long haired' which appears to include two types of coat length (long or semi-long) but I can't find any other breed standard - where do I find that? Have you spoken with UK breeders about the smooth-faced variety? Perhaps they can tell you if they pop up occasionally or put you in touch with their overseas contacts
I've never really heard of this breed before so thanks for putting it on my 'learn' list - I realise that this is probably the breed of dog I spotted in France once. I saw a woman nr Carcassonne with 3 (full face hair) but lacked the language skills to ask her what they were!
Kindness is the language which the deaf can hear and the blind can see ~Mark Twain