For the next two years or so, while Britain negotiates its post-Brexit deal with the EU, nothing will change for British citizens living in France.
It is also likely that existing British residents in France will be able to continue living in France after Britain leaves the EU. Some lawyers argue that if you have lived in France for a while you will have “acquired rights” under the 1969 Vienna Convention which says that the termination of a treaty “does not affect any right, obligation or legal situation of the parties created through the execution of the treaty prior to its termination.”
The House of Commons Library says that “withdrawing from a treaty releases the parties from any future obligations to each other, but does not affect any rights or obligations acquired under it before withdrawal.”
Nevertheless, nothing is sure. If Britain expels EU citizens living in the UK, as UKIP-type Brexiteers want, EU countries could take tit-for-tat measures.
One step you can take now to protect your right to remain in France is to apply for permanent residence. Unlike French nationality, which is discretionary, if you have lived in France for five years or more you have a right to a permanent residence permit.
The titre de séjour permanent, (also referred to as UE séjour permanent, toutes activités professionnelles or carte de resident ) allows you to live and work in France and enjoy the same rights as French citizens to benefits and healthcare. It does not, however, give you voting rights or allow you to hold public office.
The card is automatically renewable every ten years as long as you continue living in France; you lose your right to the card if you are absent from France for more than two years.
You will have to apply in person to your local prefecture. You will need copies of your birth certificate, passport, tax declarations and bills, such as your electricity bills, to prove you have lived in France full-time for a minimum of five years. However, prefectures differ in exactly what documents they ask for so it is as well to contact them and find out before you apply.
As an EU citizen you do not need to provide proof of work or income to apply for the card. The EU website states clearly that the card must be delivered as quickly as possible and that you should not be charged more than the cost of a standard identity card:
Les autorités doivent vous délivrer le document dans les plus brefs délais et moyennant des frais ne dépassant pas ceux demandés aux ressortissants pour la délivrance des cartes d’identité.
If you run into problems, contact the EU complaints department here.