I stayed in Hostal Gislay. I paid 20€ for an individual room but was "upgraded" to a double.
The small double room had no external windows and was very dark. Very little street noise as a result. The beds are the low end style you often find here where the springs are felt through the matress. Linens appeared clean. TV, but no phone. Small armoire with only a few hangers.
Biggest issue is the shared bathroom. It is very tiny, which would be ok if it were in the room, but I expect more when it´s shared. Cramped, and hard to move around in, often missing toilet paper. The shower was awkwardly designed, to where you will unavoidably freeze yourself after bumping into the faucet handle which is in a bad position. Outside of the shower there is barely enough room to dry yourself off.
Overall I would say it´s very cheap but manageable in a pinch. I think if you go up to 25€ in other hostals for a single it would be a worthy upgrade.