You have my sympathy. I too have a Clio 1.4 16v which will not start. The battery drains to such an extent that the immobiliser kicks in and then jump leads will not work. You will need to reset the immobiliser then put jump leads on it. (Don't ask me how to reset the immobiliser, I haven't worked that out yet, it's something to do with the key!!) As to why it's doing it, I'd like to know that too! I'm in not so sunny Devon, not the Alps so not that cold here. I hadn't driven my car for fours days and it was as dead as a door nail. I had a new battery two months ago and my local garage can't find any drain so I'm stumped.
I have noticed that my clock stays on when I've turned the ignition off so wondering if that's the problem. It's VERY frustatrating to say the least and costing a fortune in garage bills!
I'll be interested to know if you get it sorted out! My Clio goes into the garage tomorrow (again) so if I learn anything I'll let you know!