Another option is to go scheduled Heathrow/Istanbul/Dalaman. I've done it a few times and it's OK, you can usually get flight timings to tie up fairly well. Look on the Turkish airlines web site or you can book them through airmiles. You don't have to have any airmiles to book with them. I think Easyjet are only going there during the summer months.

Hi, Turkish Airlines is showing a price of £308.56 per person for February 2009. This is from Heathrow to Dalaman via Istanbul.

i beleive easyjet has not released flights to dalaman 2009 yet i have been looking and waiting to book for summer next year

Hi there i have emailed them and asked if they are running flights from Gatwick or Manchester for Jan and Feb 09 and when they will be released.
Hopefuly they will as everyone else is soooo expensive just now.