@Walter Hinteler,
I haven't thought about this at all before, but British expatriates in France, Germany and elsewhere in the European Union will suddenly find themselves on the outside with no say from tomorrow night onward: they will loose the right to vote and stand for office.
The right for all EU nationals to vote and stand in municipal elections where they live, even if they are not citizens of that country, was enshrined in the 1992 Maastricht Treaty which established the EU. (Some countries allow non-EU citizens to vote in municipal elections. So even after Brexit, Britons should still have a voice at the local level in Denmark, Finland, Sweden, the Netherlands and in two cities in Slovakia. In Finland, they will need to have been residents for two years, while the residency requirement is five years in the Netherlands.)
Since McG has a special interest in the next war of France: 757 Britons serve on municipal councils in France, and they will keep their seats until municipal elections in March.