Hi,
Amoresperros - I think you must have been a little unfortunate in your experiences in Tunisia re food and drink! In my many trips out there I can safely say that I have had fantastic meals for next to nothing - certainly much much cheaper than anything of the same standard in the UK. Though as with anywhere that sees a large number of tourists there are plenty of places that leave a lot to be desired. It seems you may have found a number of these!
Kevin - I totally agree with you. In Tunisia the best food is Tunisian. Makes sense to me! I see so many people at the hotel buffets trying to find what most closely resembles what they eat at home. And usually there's a fabulous Tunisian speciality on offer most evenings.
Mike - I've never been self catering but would imagine trying to shop for things out there would be quite difficult, especially given that us Brits are so used to popping into our nearest Asda or Safeway and getting everything we need in one go. The shops near the hotels will be overpriced as they are targeted at us 'rich' tourists. I suppose this is the equivalent of our corner shops - so much more expensive than the big supermarkets.
If you're feeling brave and are good at haggling you can try the markets. The main market in Hammamet is on Thursday morning. A bit further away the market at Sidi Jedidi is on Tuesdays - some tour operators organise excursions there now. But be warned - it's busy!
The 'supermarkets' are Bon Prix, a long way from where you're staying, in Jinene Hammamet - and the prices really aren't that good and the Magasin General in the centre of Hammamet. However, don't expect anything great from this! You'll be able to buy water, fruit juices, pastas etc, but it won't be anything like shopping at home. It is the only place in Hammamet, other than hotels and bars, where you can buy alcohol. Though remember that Friday is the Islamic holy day and the alcohol section will be closed.
Imported spirits in Tunisia are expensive, especially compared to general prices in Tunisia. However, I've rarely paid more than I would pay in the UK. As an example in May I went to the Habana disco bar in Hammamet with my boyfriend. Over several hours we got through 3 half bottles of wine, 2 or 3 vodka and cokes (larger measures than the UK) and 7 or 8 bottled beers (yes we had hangovers the next day

). All that came to about £40. And it came with constantly replenished baskets of popcorn and other snacks. I usually take a bottle of something from duty free to drink of an evening on the balcony and a second as a present for my boyfriend. I've never been stopped and checked at customs in Tunis, but I wouldn't tempt fate by taking more. Technically there shouldn't be a problem with taking stuff bought here in your case, as the taxes will already have been paid - though that's only a guess.
I get the feeling you may well be wanting or needing a restaurant at some point! Near the Aziza is the Marco Polo. It won't be getting any Michelin stars any time soon, but it's decently priced and the couple of times I've been there the food has been good. There's another restaurant next door to it called Arabesque, though not having eaten here I can't comment on prices or quality.
Hope this is of some help. Any more questions let us know.
A.