I had a Sony adaptor in my 95 16v (still have it if anyone wants to buy it, digs it out of cupboard, its a PC9-101).
It has one connector for the head unt and another for the original remote connector. There is enough room behind the HU to leave it there, its a doddle to fit (replying to adis question here for an original Clio so no upper dash out), remote functions work a treat, can even do more than the original Renault one including turn the head unit on and off !
Its a little black box that converts the contact closing combinations of the renault multipin remote into different resistances for the Sony 3 pin interface, more trouble than its worth for DIY.