Suggestions - quality spa/relaxing massage/hammams (Tunis)

I have a female friend coming to visit and thought it would be fun to organize a relaxing day or half-day at a spa or nice place with relaxing massages and/or hammam/thermal baths.

I've seen a few places (like Villa Didon) listed, but have no idea as to the actual quality of the experience.

All suggestions & reviews are welcome for the best places in Tunis, Hammamet, Sousse or Mahdia. An idea of price is also appreciated.

Many thanks in advance.