You're welcome. The band "Soldat Louis" was founded by Serge Danet (aka "Soldat Louis"-the guy), lead singer and Renaud Detressan who plays the guitar and writes their songs with or without Soldat Louis- the guy. So the song was indeed recorded by Soldat Louis -the band- and written by Renaud Detressan and Soldat Louis-the guy. It's mentioned there on their site.
The cd "Première bordée" I mentioned above is their first album.
I don't know about this particular song in Brittany but the band is famous all over France.