In reply to Potemkin:
I've used Rob Jarvis at High Mountain Guides before and would definitely recommend him.
I've also heard good things about James Thacker and Jonny Baird, but haven't been out with them.
Not sure if you've sorted accommodation yet, but Chalet Breezy is run by a UK couple whose love and knowledge of skiing in the Chamonix area is just incredible!
Enjoy your trip!
Calski