I cannot recommend anywhere but have yo tried the internet. There is sure to be some accomodation advertised on the Pamukkale or Denezli websites.

Failing that try Rough Guide or Lonely Planet.( the prices are often out of date )
You will then at least get some sort of guide price

There is a range of accomodation ranging from cheap Pansiyons through to 3 star and 3 star plus hotels.

Thanks Apollo ... I've already tried the options you mention, but personal experience is always helpful to decide between the various pensions listed.