Thanks for the replies. In the meantime I have ordered in Poland the "Atlas Agroturystyka" from the Polska Federacja Turystyki Wielskiej, which seems to be what we want. However from the part I saw on their site, it looks like the offers are quite limited in the Bieszczady region and mainly focusing on some kind of collective accommodations. Dorm rooms were fine and fun when I was younger ; nowadays having over 50,000 km on the meter, my bones require a good bed and a pierzyna !...
;-)