They are quite fly (no pun intended
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) with their pricing, the return flight is only a total of £60 it is the outbound flight that makes it almost £200, that flight on the 3rd looks to be the first flight going out for the season.
Aslemma I don't know if that is the only date you can go however I have tried looking at a few other date combinations but the return prices are then creeping up, it does appear to be around the £200 mark for both flights including 20kg luggage.
Just a though try booking the TC flight through this
http://www.skyscanner.net/ and see if that works
IMPORTANT the flights leave UK on the Sat however it is early hours of SUNDAY morning it leaves Tunisia so search for example -
Depart Stanstead Sat 3rd May and return on Sun 18th May
Graham
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PS, Is it Internet Explorer you use to browse? if so try using a different browser such as Google Chrome, Safari or Mozilla Firefox and see if they work better.