I spent three years in France for personnal reasons and i will come back there soon. For gyms it really depends on what you're focusing on. The gyms Jard.the.gymnast gave have one- two elite but not more. There is great and big gyms that are really good in the level corresponding to L9/10. French elites do not train in gyms but in national training centers.
If I take the list before and keep only Elite/Developmental big gyms:
Avoine Beaumont (about 60 km from Nantes)
Meaux Gymnastique (close to Paris)
Indépendante Stéphanoise (near Lyon)
(Elan Gymnique Rouennais (60 km northwest of Paris)) - > they used to be good but they mostly have gymnasts coming from other gyms after becoming elites
Union Haguenau (near strassburg and stuttgart, so close to Germany)
I'll have to add:
Alliance Dijon Gym 21 (middle France, between Paris and Lyon) they have olympians and national team members every year. The city is very nice
En Avant! De Paris (more a L9/10 thing they have really good equipment but their gym is going to be under construction next year). That gym is in Paris. The high level girls are thinking about moving either to Clamart or Puteaux (western paris girls) and Sucy en Brie and VGA Saint Maur (eastern girls)
Club Athletique de Combs la Ville (close to Paris)
The region Alsace has many big gyms including Independante Kingersheim, Gym Mulhouse (their gym is really nice), Union Haguenau, La strasbourgeoise, Gym Saint Louis, Wittenheim, Illkirch-Graffenstaden, Obernai and i probably forgot a lot. The life there is really nice, it's hot in summer but mountains are near and Germany and Switzerland too!
Also in Middle France, between Dijon and Avoine-beaumont you have SM Orléans (they currently have an Elite, their first one)
In the north one of the big gyms in Hénin Gym
In the south ASCM Toulon has a good team but lost their national training center a few years ago
In the East Metz Gym is located in the city of Metz near Germany and Luxembourg
In Paris suburbs there are some nice gyms but life isn't really nice in those cities.
Those are a few gyms I thought of.
One more thing that you need to be careful with: Gyms in France are often closed on summer for a few weeks and you'll only know that after contacting different gyms.
If you need any help don't hesistate to contact me. I may have forgotten some gyms but there is good gyms in every region of France. I don't know so much about West and Southwest Gyms as i didn't compete against those gyms. However, i still have some friends that can give me information about it.
One last thing: Gymnastics words in France come with training. I came here not knowing any gymnastics word but girls are really happy to have international teammates.
