Ok, what I need to know is does any one know if any of the peuget's have a trailing arm length of approaching 400mm from pivot to centre of stub axle.

Do you mean on the older 205, 309, 405 models?

Never measured them, but I'd say they're closer to 300mm than 400mm.

Trailer building per chance?

keep in mind a lot of them are shagged, or on the way to it. the bearing design is rubbish so they wear in one spot and you end up with ridiculous camber!