Just had a call from a young lady from Hellas Jet informing me that the company is 'closing down'. I had booked return flights to Athens in July and September with Hellas Jet. The September flights I booked on 29 March and wondered why they had not taken payment on my credit card yet- now I know! I have been offered a full refund for the July flights (will take 21 days) but unfortunately finding replacement flights (either BA, Olympic or easyJet) is going to cost significantly more than I originally paid.
Looking at the Hellas Jet website it seems they cease operations on 10 May - looks like they simply couldn't compete, which is a shame as they provided a good service at a reasonable price (obviously too reasonable!).