For what it is worth, I thought I would comment on what British passport holders, resident in the #Schengen area will face if the United Kingdom really does exit the EU.
Several months ago I was hearing how a number of Brits in Crete were rushing?? panicking?? to get their residents permits sorted. Many have been living in Greece for a number of years without actually getting the document.
Local Crete experiences have shown that local police were being relaxed about people not having the document unless you got into trouble (speeding tickets etc). Still the law states that an EU citizen of another country has to have a residence permit after staying in the host country for three months. For all practical purposes the document seems not to be required and the passport is the first preference, when asked. Notable exceptions have been in buying a car. Although I hear that has changed.
Here is what I would say if it were me affected, without being a lawyer or a professional advisor. If you are living in Greece (or any other EU country on the Continent) get a residence permit before the UK makes any formal move on Article 50 of the Lisbon Treaty. This is formal process of leaving, with a 2 year window to do so.
In this way, you would be on the Schengen shared information database for police and security matters. You must remember that living in the EU, foreigners with the right to live there have freedom of movement throughout the whole area, once they are resident in one of the member states in the zone.
#Schengen covers all EU countries (including non-EU of the European Free Trade Association – Switzerland, Liechtenstein, Norway and Iceland) except Bulgaria, Croatia, Cyprus, and Romania — and of course the UK and Ireland are outside. See map below.
So for those 1.2 million long term Brit expats staying in Schengen countries, just be prudent and make sure you have backstops in place to avoid bureaucratic hurdles in the future.