Not many responses here is there.....
Firstly you need to consider the likely draw, then consider the distance between the battery & the starter.....
An average starter motor will pull around 20amps unloaded, (as in sitting on a bench spinning itself), but spinning an engine is a different kettle of fish.....
I would expect the draw to be anywhere from 200amps to 350amps, (may well be more but I'm not familiar with the Clio's), a quick check on the stock battery specs will give a clue, (check the CCA rating).....
There are a few issues which should be addressed to ensure you maintain a safe charge circuit, (also don't forget to inform your insurance company who will possibly request proof its safe).....
The battery will need to be firmly fixed or clamped down & of the sealed variety, (unless housed in a sealed container with venting to the outside of the car).....
Any cable which passes through the bulkhead that has a power supply needs to be fused, (which means that the alt/batt charge lead needs fusing in accordance with the alt output & cable rating).....
4awg over 12 feet shouldn't be fused any higher than 125amps based on safety, based on voltage drop it should be fused no higher than 80amps.....
I would go with 0awg power cable throughout the start/charge circuit, some will state this is overkill, I would state its safe.....
The starter draw would only last a few moments, (hopefully), so I would start with a 150amp fuse, (which should support short bursts upto well in excess of 250amps), but not exceed 250amps, again based on safety....
The above sketch is merely an example of how I would go about relocating the battery in my car, as I stated earlier I'm not familiar with the Clio so you may not require all the under bonnet earths or fused feeds.....