1. Do I need an Altiport rating as well as a Mountain rating or does the Mountain rating cover specific Altiports too? How many hours are each rating?
You need either a full mountain rating, which is currently valid for life at all altiports and altisurfaces with no currency requirements, or you need a site authorisation for Courchevel which needs to be renewed by experience by landing as P1 once every 6 months, or renewed by flying there with an instructor who also holds a full mountain rating.
To learn to fly a circuit safely at Courchevel in nice weather takes a few landings and perhaps a couple of hours. Some instructors will give you a site authorisation after that. To do it safely, you should also spend a couple of hours learning to fly and navigate in the mountains, and experience different wind conditions - typically a sign off for your first altiport from a thorough instructor would take 5 or 6 hours flying.
The full mountain rating is quite different, and typically takes between 15 and 30 hours training for the wheels rating, and about the same again for the ski rating.
Chambéry is the sensible place to fly to if you don't have the rating, as long as you don't want to park there on a Saturday when the British charters arrive.