Ours has just gone too, as the cold weather kicked in.
There's a batch of Megane's with problematic radios -somewhere between 2005 and 2007. There's a temperature sensor that fails if it goes below -5 degrees (seriously).
Renault will repair FOC if advised, although there's a bit of a queue at the moment.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix in-car audio.