Hostel Fish is an affordable & practical option in a good central location, with a communal kitchen & bar, safe locking storage for belongings, and sparkling bathrooms, all in a fascinating antique building, sensitively remodeled into a hostel.
The mattresses are way too soft for me, but a yoga mat or camping pad or two on the wooden platform would serve just fine, though you would have to bring your own, unless they decide to get a few. The blankets, which they call duvets, have clumps of stuff inside interspersed with large areas of absolutely no contents, so very lumpy, and not insulating in the void areas. Fortunately for me only a sheet was needed, as I stayed there in summer.