Hi, and welcome to the forum.

OK, you're coming from Britain, so you don't have the visa hassles to worry about. But where to start kind of depends on what exactly you're planning on doing while living in France.

Will you be working? Or is this part of your retirement plans? If you're going to be working, you may have to tailor your location to the type of work you do because, as has been explained elsewhere on the forum here, finding a job in France can be a real "challenge" - especially for foreigners.

If you're not bothered by working (lucky you!) then do you speak French? The British in France, particularly those living in the south of France, are sorely resented by many of the locals - because they "refuse" to learn the language (or speak it so badly as to convince the locals they expect everyone around them to speak English), because they keep to themselves and don't "integrate" into the community, and because they pay too much for rural properties and thus drive house prices up so that young French couples just starting out can't afford to buy a home.

Now, many of these accusations are (obviously) things that the French contribute to in great measure (for example, in small towns, newcomers aren't readily accepted, so of course the Brits tend to stick together...), but they are worth considering when making your decision about moving to France.
Cheers,
Bev