I've been looking into this myself. You could of course always use Rightmove, where you write your own advert and they host it for you. However, I believe the site tends to be mostly viewed by the British, and if you search for properties on Crete via a search engine in a foreign language, Rightmove doesn't feature high up in the results. You might want to look at a French company, http://www.green-acres.com
. They are a similar set up to Rightmove but with a few important differences. For a start they're cheaper. Crucially, however, when you upload your advert and photographs, the site automatically translates it into 20 different European languages. The company claims to be active all across Europe and seems to have an excellent SEO profile in whatever language you use. Hopefully, this means that when advertising your property, you're not restricting yourself solely to UK buyers. If it becomes the case that after Brexit, UK buyers of property within the EU become fewer, a pan-European sales strategy might be the way to go. That's where my thinking is on the subject at the moment.
Hope this helps