Does anyone have an idea where I can get decent trail maps for les Arcs. I can’t seem to get os maps of this area

The French equivalent of OS maps are IGN (Institut Geographique National). I have the Les Arcs/La Plagne one sat in front of me.

It is code number 3532 ET, so a search for “IGN 3532 ET” should show you plenty of places to buy them in the UK.

You can also get IGN mapping on some GPS units, Satmap certainly do them.

As for trails, they may or may not show up on IGN maps. But if you’re going there, you can pick them up at the tourist office when you arrive. Search for “Les Arcs VTT maps” to see an example.

thats great thanks

Get a guide, seriously
Unless they’ve fundamentally revamped the signposting and trailmaps you won’t find the best stuff without a lot of effort and time using the IGN map (and trial & error)