Nico, it took me a long time to receive a response. In some cases, 3-6 months. It is not the actual letter I wrote but the time it takes for them to process the request. I did enclose a self-addressed envelope and enclosed a copy of my identification (passport or driver's license). Most of all it took a lot of patience. Some communes, from what I understand, reply rapidly in 1-2 weeks. Some also will acknowledge emails for requests but not all. I guess it is a stab in the dark. I do an email to the commune if an address is available and then mail the letter. Don't know if this has done me any good but at least I tried to cover all bases.
You can use:
You can write your letters with these as guidelines depending on what you want to say. Some are fill-in form letters and others have phrases you may want to include. I have used a combination of these letters.
I am sure other forum members may have other sites they know of with other suggested letters.
When you do write one, be sure to post it on our translation section to make sure it says what you want it to say. I know Gente members are more than helpful in assisting you.