Although French President Emmanuel Macron has assured the citizens of the United Kingdom that they will not need visas to visit France, he did not say that those who already resided there would not be dismissed.
In an interview with the Sunday Times, Katrina Murray, 37, who works as an independent financial adviser, said: "Everyone is very scared.
"People do not know what will happen and some think they will be expelled."
Last week, hundreds of concerned Britons met with the British ambassador in France, Edward Llewellyn, in Bordeaux.
He admitted that he could not put an end to his fears, saying: "There are some problems, many problems, for which we still do not know the answer".
Previously, UK citizens did not require a visa to live, work or study in France and, for many years, the slow pace of life has attracted older expatriates to rural areas and the coast, while Young professionals are attracted to expensive cities such as Paris and Lyon.
But while British expatriates in other parts of the continent may face some uncertainty about the impact of Brexit, France's are in a unique position.
European citizens are not required by French law to register in the country.
To determine their right to remain in the country, UK citizens will have to show how long they have lived there, something that can cause problems for those who have not paid taxes.
Brexit can also affect UK citizens who own property in France, as it can cause a change in inheritance laws and taxes.
Brexit junior minister Robin Walker has asked France to guarantee British expatriates the right to remain to alleviate their anxiety.
A bill that gives the government the power to adapt or suspend the need for residence permits and visas for the British has been presented in the upper chamber of the French parliament.