Hot spot is Hergla Corniche, a few miles north of Sousse. We've just bought a 2 bedroom luxury flat with fitted kitchen, marble floors, air cond and with fabulous views over the med for £38 000 approx. When the planned development of a brand new holiday center with hotels, marina etc is completed values will almost certainly double.
In the long term the government needs to make it easier for foreigners to buy. If they do prices will double again.
The best site to find properties is in French -
www.bourseimmo.com.tn.
Good luck