We have rented a house near Nyons (Drome Provencal) every May/June for the last 15 years and are considering opening a bank account there. I'd appreciate any advice, tips, information from those of you who have done this.

It's difficult to do without demonstrating you have a French address. The classic proof is a utility bill, which obviously you won't have. I'd suggest asking your lodging providers if they would write a letter "d'hebergement" for you. One sentence will do, certifying that they're providing you lodging, and where. They need say nothing about for how long or under what terms. We've done this occasionally when we've had renters staying long enough to have interest in establishing French accounts, and we've attached a copy of OUR utility bill for the address, and one of our French residency permits. This has worked.

Then start making the rounds of banks. Don't drop in. Make an appointment.

Dave

good advise from Dave.
the certificate is for a better translation a certificate of Lodging.