In reply to Cazt: Masterclass gets good reviews. Was run, and maybe still is, by Stuart Adamson. He also teams up with other local instructors. You'll get proper technique explained in some very effective ways. He did wonders for my mogul skiing; some years ago now and he was 61 years old then!
If you can afford private lessons, even if only a few, imao they are much more productive than group ski school.
There is also an instructor based in Vaujany just over the hill from ADH called Christelle. She will gladly meet you in ADH. I can't remember her surname but the last number I have for her is +33 6 83 14 05 74. Her English is excellent.
ADH is a great beginner resort, loads of big wide easy angled slopes, some free lifts and you can get up to the glacier. The views up there are fantastic. The runs on the glacier (which is crevasse free) are blues (and black) so may give you a challenge depending on how quickly you make progress but it's worth the trip up there on a sunny day just for the views (assuming the lift pass option you decide to buy will get you there).
We learned to ski there, our kids and grand kids all learned to ski there. When we visit we always stay in Vaujany. The area has many happy memories for us. Hope you have a good time.