cheap airlines around new years....

hi, i have kinda boxed myself into a corner here and i am going to have to do a fair amount of travelling in the days immediately before and after new years. easy jet doesnt have flights posted for that time yet. i was wondering if anyone knows how much flights go up around that time. is it going to be impossible to find those 10 pound flights or are they all going to be really expensive ? ill be flying from athens to london around the 29th dec and then london to copenhagen around the 2-3 or jan.
thanks!