UPDATE: I appreciate that things change but thought I'd post today's experience for anyone who may find this of interest or use.
Today we visited our Notary in Chania and signed our Cohabitation Agreement. Prior to that, upon contacting our Notary last month in this regard, she sent us a template/draft of an Agreement in Greek. We have conversational Greek but this was legal jargon and so we had it translated by our teacher of the Greek language. From this template we were then able to decide which elements we wished to have included and excluded in our tailor-made Agreement. For example; because of our ages and the fact that we have lived together for 17 years, we knew we would not be having any children together and thus minimised that particular clause by saying that any issue would take my partner's surname (the clause could not legally be excluded), also I did not wish to take my partners' surname and so that was stipulated, all of our property is in our joint names and covered by our Wills and so reference to the detail of this was excluded in our Agreement. The cost to us was 120 Euros and in addition to that we paid for four copies at 10 Euros each. The original document is kept at the Notary's office (she also has our Will, so it's nice and tidy), the four copies we have are stamped and signed copies.
Living within the Chania District, we now have to take one of the documents to the Municipality of Chania offices (close to the Bus Depot) to have the Agreement registered. They keep that copy. Unfortunately by the time we'd finished at the Notary's office the MofC offices had closed (opening hours we are advised as between 9am - 1pm).
We can then visit IKA in order to obtain an IKA book for myself. I arrived in Crete with an S1 form (not technically correct because I was 52 when we arrived in Crete so it was an S-something form, where I had an IKA book which lasted for two years). My book expired because my partner and I are not married and I could therefore not be added onto his book. Hence going down the Cohabitation Agreement route.
Again for the record, the Cohabitation Agreement is a legally binding document and we had to declare that we were not otherwise related, by adoption or birth, were not married to others nor had a Cohabitation Agreement with anyone else. To dissolve the Agreement we would have to return to the Notary and declare our intentions, she would then draw up a document to this end and we would then have to take that to the Municipality of Chania offices to have that registered.
Interestingly, should we ever decide to become Husband and Wife, we would have to have our Cohabitation Agreement dissolved first (see above paragraph).
Someday is now : )