It’ll be a 2 year wait to know for sure what the consequences of the March 29 Article 50 letter will mean in reality for expats.
Personally, I’m hopeful but not optimistic — especially for many British expats in limbo situations.
Those of us who have worked in France for many years will be fine, but the fate of some other expats is up for grabs.
No Briton will be expelled because of Brexit, although resident cards may become obligatory as they once were (and still are for non-EU citizens - which Britons will become in 2 years).
Some people may find they have to return to the UK because of the falling value of their Sterling incomes, or the fact that they could lose their reciprocal healthcare rights.
These reciprocal healthcare rights will become a big issue for some. Even if you are a resident paying council and income tax, note that having healthcare rights is not directly related to this.
If you were/are employed by a British (or other EU) company, you have had NHS cover because your employer paid NI on your behalf - or you paid it if you were self-employed. This entitles you to emergency care anywhere within the EU through the EHIC system.
If you are a legal resident paying tax, but not NI, in France, the French want to be sure that they will be reimbursed for your care. This is the case (at least until Brexit finally happens and perhaps afterwards) for Britons of retirement age that were previously covered by the NHS. French retirees in the UK have a similar right as do Britons of retirement age everywhere in the EU. This is probably about to change, but not for 2 years.
a/ You are paying French National Insurance because you are working in France. You are covered and will remain so.
b/ You are of retirement age and were covered by another EU country’s healthcare system such as the NHS.
c/ If you are covered for emergency care (but not long term care) by the EHIC card because your healthcare depends on the NHS, you should request this card from the NHS. But this card is not for long term care, if needed. It’s for emergencies only.
d/ You are covered by the provisions of the S1 form and therefore qualify for a Carte Vitale as an EU citizen and EU resident. You should ask the UK for that form. Its future usefulness in 2 years is unknown but it will cover you for the moment.
e/ You are voluntarily paying into the French system through something like the CMU (Couverture Maladie Universelle) or PUMA. The bureaucracy is complicated, but sometimes possible.
f/ You are the spouse or civil partner of someone who is covered in France - usually someone working in France or retired under the reciprocal EU arrangements which may or may not end it 2 years’ time.
g/ You have private medical insurance. This is sometimes affordable while you are young but becomes increasingly expensive as you age.
Points b, c, and d above are up for grabs after Brexit becomes a reality in 2 years. Much will depend upon whether or not reciprocal healthcare and EHIC rights remain or not. This is a complete unknown at the moment.
If in doubt, you should get expert advice from someone used to dealing with expat situations.
For the paperwork, for as long as the UK is still in the UK: