I've flew to Tunis a few times but think that Monastir is handier for Sousse. Again all depends on flight times as I have had 7am flights back to gatwick before which means being at the airport between 5 and 6. Not too bad as we can stay with his family in Ben Arous but would be a killer from Sousse for me - I am sooo not a morning person. If you get good flight times then I don't mind it at all. I probably hate it more as have to connect again to Glasgow at London but Monastir I can get a direct charter. Tunis gives more choice in day of the week to go on from certain destinations though (like Glasgow)
