France

[Torchwatch]

I've only been to Cap d'Agde once. It is a small naturist resort city.
On the beach and in the pools everyone is naked, you can go anywhere within the area naked if you choose, this includes the shops.
In the evening people dress for partying in the bars and restaurants, they dress for effect rather than conventional decency and bits are often on display.
It is an experience but not really a place for speedos.

Since shorts are generally banned in French swimming pools wearing speedos on a beach or around a campsite with a pool is not unusual.

In French towns you sometimes find road signs banning speedos on roads inland off the sea front, without the ban people would wear speedos in the town center.

I have hike, cycle and car camped around the French coast, mostly in Northern France, Brittany and the Bordeaux coast. You'll be comfotable in speedos in all these areas. With the Channel Tunnel and high speed trains you can get to the Bordeaux coast in a day from Kent.

You can explore Northern France and Brittany by taking a ferry with a bike or car.