I stayed at the Grand-Séminaire du Puy for two nights at the end of September 2014 in a large single room with a sink (showers/toilets down the hall) for 22 euros, including breakfast. There were only three guests in the whole huge place at that time, and dinner was in a homey dining room with the small monastic 'family' that lives/works/studies there. I enjoyed my stay because I love big old rambling edifices, but it was chilly (damp and raining; heat not on yet) and the wifi didn't work. I got the impression that not many lone pelerins stay there, that it's mostly used by large groups, and I think it might be very, very noisy when it's in full swing, because the old wooden floors are creaky and the wide halls and staircases amplify sound like crazy. So, Marbuck, you may have escaped some sleepless nights!
You asked about similar places further down the road. I highly recommend the pilgrim accommodation in the beautiful Abbaye Ste Foy in Conques (contact info in Miam Miam Dodo). There are both dorm beds and private rooms, and a wonderful dinner is served in the rectory, warmed by a roaring fire, before everyone heads to the evening pilgrim's mass. It's quite magical. Bon chemin et bon courage!