Organiser Kathy John, from the Rift in the Dordogne and Lot-et-Garonne Facebook group, said cartes de séjour and healthcare were the big topics at the meet-up in Bergerac.
She said she has met only “one or two” Britons in the area who voted for Brexit.
“What is more, those of us who have been here more than 15 years and couldn’t vote feel this is imposed on us with no choice at all,” she said.
The rally was attended by British residents, as well as local French people and French partners of Britons, she said.
Reactions were positive from French and British locals, she said, though a British woman on holiday said they were wasting their time as Britons in the UK just “want to get it done and get out”.
Mrs John said: “I wanted the French to know we have no quarrel with them and have always found them friendly, welcoming and helpful, but to be more aware of what we stood to lose, and the difficulties we would face if there is a no-deal.”
The cartes issue is especially worrying, she said. In the Dordogne, there is a system of booking online for an appointment to submit an application.
“I know elderly people who are not internet-savvy and can’t cope with the fact that you need to collect a lot of data, much of which is only available on the internet unless you are very mobile and can get around seeing different bodies, and appointments are only available online.
“In addition, there have been no appointments available for months and many people try on a daily basis. Some are lucky, perhaps due to cancellations, but perhaps the policy is now to wait and see as if there is a no-deal people will have to exchange cartes for new ones anyway.”
She added: “People worry about not fulfilling minimum incomes, especially since the fall in the value of the pound.
“And the elderly rely on S1 forms for their healthcare and we don’t know how long they will continue in a no-deal. Will they have to go back to the UK and find an old people’s home?
“There are lots of vulnerable people who are fine with arrangements now but will not be if they lose their healthcare.
“Younger people worry about the right to work and if their children will be able to go to UK universities. There are a mass of issues putting an incredible strain on families.”