As far as I know, if you have a residence/work permit that should mean that you're already registered.

Thanks a million for that, Edward! I was hoping that would be the case.

As EU citizens, you don't even need a residence permit; you have the right to establish your residence wherever you wish in the whole EU.  However, you should check with the UK government whether you need to declare to them that you moved to France.  Some countries require it in order to keep a record of all citizens abroad.

TheOmegaMan is right. I had to declare in Greece that i moved to France and then i went to my local Mairie to register. You don't need a residence/work permit, just a valid passport or identity card and the contract of the house.

thanks for your replies. We are currently waiting for our Frontalier permits (my husband works in Geneva) - his HR department applied for it. When that comes through, does it mean we will be automatically registered in Switzerland as well as France, or does it only apply to Switzerland? 

The UK knows we're in France.

Anna, if I still have to go to the Mairie, what do I tell them? Our French is almost non-existant. I'm still at the beginning of my lessons, so I'll have to write down what I need to say to them.

Thanks :0)

I know that if you bought the house where you are living now you don't have to go to la Mairie, if you rent it i don't know.

My french isn't good at all but you will manage to communicate with them saying something like " nous vivions en Angleterre, mais maintenant nous avons demanage ici. Je tiens a declarer que nous vivons dans cette adresse ",  and then you give them the contract of the house and your passport. That means that you were living in England but now you move here at this adress.  

Everyone who knows much better that me the language feel free to correct me. Hope that helps.

great, thank you!