We have a diesel combi boiler fitted in our villa, it runs 8 double radiators and if we want we can have the hot water with heating or without.
We fill a 100 gallon tank, this can usually last for 2 winters (filled tank November 2006 approx 1000TL and topped up 300TL November 2008, total cost between £500 and £565), the pipes underfloor give us extra warmth acting like a underfloor heating, Uzumlu is much colder than Fethiye and how you use the system and for how long of course will depend on cost.
Boiler make is Baymark, we have had the system 6 years and no problems, the only place that did the heating system at that time was Beko, a few friends have since used the man in Tasyaka and they are happy with his services.
Although Gordon comes from Scotland and should by rights be used to cold, he turns the heating on whilst me, the "Soft Southerner" turns it off! however, I would not be without it during the winter.