The following images and notes are based on the project originally described on the Jeanneau Owners Forum.
It is reproduced here in edited form by permission of the author.
I have the standard Jeanneau fitted double light switches in my saloon cabin ceiling of my Sun Odyssey 419.
I wanted to replace one or both switches with a dimmer.
After some research, I found the units are part of a range made by Inprojal.
They make both a dimmer and cover. (Scroll to the bottom of these links)
After I bought the dimmer unit, I tested it prior to installation to ensure it worked with LEDs.
The Inprojal insert series are interchangeable with Berker (who make some of the electrical components used in others Jeanneau's)
The unit was also advertised for compatibility and it is size-wise, but I had to trim the mount a little.
The wiring took a little working out, both the negative 12V wires have to go back to a negative. I used the negative terminal on the other led lamp in the same panel. All the LED lamps go back to a single fuse on the main board.
Pleased to say it is now all working.
Ian - SO419 - Tumbleweed - Croatia
The original thread may be viewed here on the Jeanneau Owners Forum.