I am a UK citizen and now live here permanently. Do I need a carte de sejour? If so, where do I go to get one.
Almost certainly not (there are some circumstances in which EU citizens do need a Titre de Séjour, but these are vague).
For more info (including where to go for a Titre de Séjour if you want one, even though it may not be compulsory):
As I said before, there are circumstances in which you need one - but you will generally be told if it is so. Although the overall requirement has been dropped, there are still some elements of French legislation (including that related to the running of certain forms of business) where a titre de séjour is still required...
Unfortunately, we're still waiting for the decree from the Conseil d'État clarifying this.
yes yes and yes