I looked in some parts catalogues and the 205 and 405 have different partnumbers... so I guess it won`t fit.

Theres a post on the general discussions page on this subject, he got a renault 5 boss to work with a little modding.

I've picked up a boss for a 300 series car for about £30. I'll let you know what I can about it when it arrives!

cheers

James