See my thread here -
http://www.cliosport.net/forum/showthread.php?544408-Heater-fans-won-t-turn-off-resistor-pack
My symptoms were that the fans were stuck on full blast, however not working at all is also the same problem. It's the heater resistor pack, around £120 new from a Renault dealer (not much cheaper, if at all, from traders on here). You can easily fit it yourself, it's not complicated, but can be a bit fiddly.
It's located underneath the scuttle panel to the left of the windscreen wipers. It's bolted down with 2 x 6mm bolts, when you undo these you can pull it out. You'll need to unplug the cables running into it first though (well, you can do it after, but it might get in the way of undoing the bolts as it's quite tight in there).
You could buy one from a breakers for about £70, but be warned that they are a common problem it seems, so personally I'd buy new (I bought one from Clio Spares and it didn't work
).
I've also read about people who are handy with a soldering iron being able to fix them for about £5, so perhaps someone with the know how could help you out if you sent it to them.
Hope that helps.
It's the bit at the top right here, to the left of where the wipers are attached (not my photo)