Ok, so here's the follow up and conclusion to my original post. My wife changed her KTP and KK to where she owns land in Bali - but this is in a different area to where we actually live. I subsequently got a Surat Domisili from my wife's 'new' banjar and a Surat Tanda Melapor from the local police station. At the Catatan Sipil I was then able to get SKTT even though my Itas, a copy of which I had to submit, clearly stated that I lived in a different address than my SKTT application.
Interestingly we were required to meet the Kepala Dinas at Catatan Sipil for a friendly chit chat while he signed the SKTT. I thought he was going to ask about the discrepancy in the addresses, but he didn't. So, a workaround, yes, but not an ideal one. In any case, I will proceed to imigrasi in the near future to apply for Itap and expect to have to explain the situation to them, as SKTT is required for the Itap application and no doubt they will see that my SKTT address is different from my imigrasi declared address - i.e., where I actually live.
To conclude - In Gianyar Regency, if you are on a WNI spouse sponsored Itas or Itap, in order to get SKTT or KTP-OA your spouse's Kartu Keluarga must have the same address as your Surat Domisili. If not, you have to either get him/her to change their KK to the banjar where you reside (good luck with this - most won't do it unless the spouse owns land there or you have been living there for at least 5 years), or obtain a second sponsor (your landlord if they are local, or if not, any other stiff from the banjar willing to be your guarantor), otherwise you won't get SKTT or KTP-OA, in which case you can't apply for eventual renewal of your Itas or Itap in Denpasar. Also note, in the case of KTP-OA, that your sponsor (whether your spouse or somebody else), will need to submit their original KK along with your application, and that if approved you will be placed on that person's KK. So in Gianyar Regency it's quite possible to end up on a relative stranger's KK and not on your WNI spouse's KK... Go figure...