I believe Citronella has been banned in commercial fly sprays by the EU from the 1st September this year, this has caused a problem for horse owners as they used this extensively, however you can make your own spray with Citronella.
I went on a weekend to Wales and got bitten (1 week before flying to Corfu), had a nasty reaction to it, my arm swelled to twice its size. Get to Corfu use good old Jungle formula, only 2 bites and no reaction.