QDM,
I'm based in Lyon, and fly from Villefranche sur Saone and from Megève. Private message or e-mail me if you can make it.
Alphaalpha,
Sounds like you probably went to St Roch Mayères (or just possibly to St Jean d'Arves). It's quite normal to lose a bit of altitude after take off. Take off is often the most critical part of the whole exercise, at altisurfaces. In most cases it is preferable to land with a reasonable tailwind, despite the short landing run available, so that you will have a headwind to help with takeoff. It is not easy to get used to landing at a 250 metre strip with a tailwind, all the more so when go-arounds are impossible... But it's way better than trying to take off with a tailwind on a sloping strip where you can't abort your take off run!
I'd re-emphasise your point about not trying it without an instructor. There's nothing intrinsically difficult in mountain flying. Any moderately competent PPL holder can do it. But there are a number of things that can catch you out....
Davidt,
There are lots of bilingual instructors!
Slim_slag and GRP,
A site authorisation is about 5 hours for the first one, which will include an hour or two of general mountain flying training. Subsequent ones for other altiports would be shorter.
There are no official currency requirements other than the 6 month limit on a site authorisation. However, if you are renting a check flight would be normal after 4 weeks away. For fledgling mountain pilots (like me), post-qualification flying is quite tightly controlled as well. The risk of breaking things is very high, so I have been going through a process of getting cleared for solo flight at altisurfaces, one by one - despite theoretically being allowed to go to all of them. And I wouldn't have it any other way! Each altisurface has its own specific characteristics, and a cautious approach is needed.