Two most popular places?

Could you put a bit more meat on the bones of your question, please, pawlak?

Do you want to live with an English family, or in a community of expats? Are you looking for working age or retirees?

There simply aren't the entire villages and towns of Brits such as you get on the Costa del Sol in Spain.

France is a very large place, about the size of Texas, and there are expats all over the place.

I haven't done an internet search, which would be easy to do and I'm sure you will have done that basic research before posting here, which would give a precise answer as to your question of the two most popular, my answer is based on observation and an understanding of the factors which move expats.

In France pockets will be quite diluted.

Traditionally many would flock to the south of France for the winter and many set up second homes all the way from the Spanish border near Carcassonne all the way across and through Provence to Nice and Menton. Not large groups remain as far as I know.

Groups of workers are attracted to Toulouse where Airbus is based. Other groups to Paris, for similar reasons.

Retirees often gravitate to either the south for the sun or the Atlantic or northern coasts which are well served by ferries to get them home for visits.

Then there are those privileged few who can afford to live in France and commute either daily or weekly to London. They tend to be close to Eurostar stations or airports, sometimes private airports.

In all the years I have been going to France I don't think that, except at tourist sites, I have ever heard English spoken in the street.

There are a lot of British living in parts of the southwest, so many that in one village the English-speakers wanted to change the language of instruction in the local school to English. That didn't fly with the French National Education Ministry. From what we've been told, houses are so much less expensive than in England that families have moved to this area. Fathers fly to London on Monday to work and return on Friday to pass the weekend with the family.

We spent 5 weeks in Pezenas in southwest France a few summers back and there were a great number of English speaking expats living in that area. The weather is relatively mild, the landscape beautiful, and the villages are small and picturesque!
Know that you can't just move to France...you need the proper government permissions. As a tourist you can stay for 90 days max. If you plan to live there, that's a whole different story.

I've heard there are lots of Brits in the Dordogne, at least seasonally, but no English-speaking enclaves or communities that I know of. Like Nigel, I don't recall ever hearing English spoken except by and at tourists.