Thank you Mike for your advice, I don't have the leisure to loose too much time on this issue so you are probably right. Nevertheless, this doesn't take away Expedia's unprofessional attitude : beyond not even apologizing, their refund offer is subject to a time period of 2 to 12 weeks, and would be separated into the non refundable part (100 euros per pax paid by Expedia) and the rest of the airfare itself that would come later from the airline. This is not acceptable by any means.