Fitting new head unit

I believe you will need a surround for the stereo as the standard stereo is wider than aftermarket ones.

You'll need a fascia adapter for a Megane for an aftermarket headunit. If you wish to keep your radio, you'll need to extend the radio cable from the bottom of your seat to the back of the headunit. The ISO cables have been extended so have a different plug for the standard headunit, but if you follow this cable, you'll find the original ISO cables which go into the new headunit. You'll also need another wiring loom to keep your existing steering wheel controls. If there's anything else you need help with just let me know.

EDIT: fitting the actual headunit is pretty much the same for every car. There's plenty of videos on YouTube and guides on other sites. The only thing that will be different for the clio will be the ISO cable extension which I've mentioned above and the radio aerial extension cable.

I know you'll need to extend the aerial lead from the drivers seat to the dashboard if you have the optional cabasse 6 cd radio but if you have the ordinary radio then that shouldn't be nessasery (from what I have been told)