I've mentioned this place on previous posts and it's probably on the low end of what you're looking for, jackal, but...

Check out the Hotel de Rouen
http://www.hotelderouen.net/
Double bedroom with shower and toilet : 56 euros per night

We've stayed there each of our three stays in Paris. It's about two blocks away from the Louvre. It's basically a 1star hotel. They have rooms with and without WC's. They serve breakfast for an additional cost. We've found the staff friendly. Various staff have helped us make reservations to restaurants we wanted to go to. The frontdesk is only open to midnight but they give you a keycode to get in afterhours. There's free WiFi.
On the downside, there's some paint peeling. The view towards the rear of the building is not great. There's no elevator so it's a bit of a hike to the upper floors. Some fixtures in the washroom are loose.

Also check out EuroCheapo.com
http://www.eurocheapo.com/paris/