Yeah wouldn't bother with Biarritz... I mean the beach is kinda nice, but it's overrun with foreigners to the point where the local charm and culture is really under threat. Vacant secondary residences are a pretty thorny issue all over the Northern (French) Basque Country, so I wouldn't go there unless you plan to live year-round and really integrate.
I live two departments north in Gironde and can recommend it. We've got some nice beaches, and from Bordeaux you're a 2hr train ride from Paris and 2hrs from the Basque Country and Spanish border in the opposite direction. The Pyrenees aren't too far either. Since they put in the high-speed train they've been complaining about Parisians driving up house prices but overall foreigners and secondary residences are less of a divisive issue. The neighbouring Dordogne, Landes, Charente and Charente Maritime departments are also nice, and there's cheap housing to be had if you're willing to buy a project home.
Overall, SW France offers a lot of good options for all different stages of life - I'm only in my mid-late 20s, no family, and I find there's plenty to do and a lot of other people in my demographic. My parents are about to retire in NZ, so in about 15 years I'll need to move back to be with them, but if the world doesn't end in the next 40 years, I'll be retiring in France or Spain.
