If you’re looking to stop with an MTB guiding/lodging company then ‘Trailaddiction[/url]‘ are probably about the best in the Les Arcs region.
If you don’t stop with them they still offer guiding (though spaces are sometimes limited).
If you don’t want guiding then Les Arcs has some really good route marked trails including a huge one that starts just about as high as you can reasonably go and swoops all the way down, via Arc 1800 and then onwards down, down, down, down and down some more to Bourg St Maurice.
Guiding is good and you will find great trails but some people find being guided or being with guided groups intimidating and if this is so then all is not lost, Les Arcs has loads to offer and sometimes its nice to go at your own pace rather than that dictate by a group.