Hello BranchingOut. Have you managed to sort something out now? It's a shame that BASS weren't able to help you as their instructors are great. However, there are other English speaking ski schools in that area such as LGS (www.skischool.co.uk). We had a private lesson with Tim Scott the other day and he is an excellent instructor. There's also The Snow Institute or TSI (http://www.thesnowinstitute.com/menus/main.asp) and although I don't have personal experience of their instruction I do know people who think they're great.
Anyway, hope you manage to find something and have a great time. It's a fantastic ski area and I hope you like Morzine/Les Gets/Avoriaz as much as we do.
2 years ago skied last minute with ESF at Morzine. It was ok, but big group, perhaps 15 to instructor, mixture of English and French. Skied lots of reds, had fun, tried some moguls. Limited instruction really, more like a tour guide, and you needed to ski fast (not necessarily beautifully!) to keep up. Also it's a pain that the ESF kids classes start at same time but at bottom of gondola, and if there's a queue for the bubble lift you can miss your adult group lesson start at the top (happened to me on last day but my group waited for me at top of ski lift and took great pleasure in shouting out my name at the pleny from the lifts to the embarrassment of me and my kids!!) Not a patch on instruction in USA, but a fraction of the cost too...
I would never ski with ESF again. I understand basic french but I don't understand technical ski terms in french and they don't have the words in English. So the last time I had lessons with them I asked them questions and he couldn't answer me. I would only ever go with companies that have instructors where english is their mother tongue.