Fitting a stereo into a Clio is a complete b*****d of a job, cause theres not a lot of room! Especially if you get one of the boxes for making the steering wheel controls work! You have to fart about threading wires and cables down into the tiniest of spaces! Ive fitted loads of stereos into Clios (everybody in my family has got one!) and I hate it everytime! But Ive put stereos into Escorts, Peugeots, and in my Freelander, and theres bags of room - enough to hide one of kids, if needs be!!
Good luck!!