The main differences between Les Arcs and the Uk is, funnily enough, the gradient and length of the difficult parts of the trail!
For example, even the red “XC” trail down from Arc1800 to the river below drops pretty much 1000m, the same as coming off the top of Snowdon! So managing your energy / velocity is much more important than for the vast majority of trails in the uk.
In the UK, trails tend sot get rated by there most difficult feature, so you can have RED trail that is 4km of flat, wide, packed stone track, but has a 50yard long rock garden and hence it’s a red.
In France (and even more so Italy) the trails are graded by there average difficulty, and can have features on them that would be above there average grading.