Well, I walked into the Anagrafe's office and said that I wanted to apply for residenza and asked if there is a form to fill in. She took my name, found me on her system and printed off the certificate there and then, at a cost of 26 cents. No producing any documents or evidence of finance/medical cover etc. My geometra had called ahead and explained that we had completed the refurbishment of our apartment and I think he spoke to the policeman too, so we didn't even have to wait in for him to visit and check us. I think it just confirms that the way different communes do it is different and it's very helpful to have a local on your side to smooth the way. Good luck to everyone else that's treading this path.