I’ve done 4 or 5 courses with Neil McNab and really rate them. He’s as good a tutor as you’ll find and we never failed to find some great snow. As mentioned this often meant a trip through the tunnel to Courmeyeur to play in the trees when visibility was bad. One of the benefits of Chamonix – when the weathers bad in one place it’s often ok elsewhere in the valley.
That said, they’re tough going and you’ll be expected to be of a decent standard for off piste courses.
Another alternative is to look at Cold Fusion. Also in Chamonix they sort the accommodation and liaise with a ski/snowboard school to provide tuition / guiding. I had a week there last year and even though we had no real snowfall the whole week, our guide found some amazing lines throughout.