Travel to desert (Tunis)

As it will become too hot for desert travel soon, I would like to head south in the next few days. Does anyone have helpful advice about travel south. The tourism office advised me that I could take a train to Tozeur, but local friends tell me that there is no train. Perhaps there is a good tour agency for travel south. I prefer not to be tied to a tour group, as I would like to spend a few days in a hotel down there...so any hotel recommendations?
Thanks in advance for any local knowledge offered.
JM