There is one campsite for the public in Meribel. It has limited spaces so reservations are essential. The campsite has hot showers and toilets. To my knowledge, unless it has changed, the electric supply is very basic for campers. Ok for lights etc but not full heating.
The campsite is situated at Raffort car park, which has it’s own gondola link to Chaudanne.
If the campsite is full then Motor homes are generally allowed limited stays in the car park. There are no facilities there. However if you use the campsite’s restaurant then at least you have toilets handy! The camp site is run by the Martagon restaurant owners situated at the car park.
Note: Motorhomes are not permitted to camp overnight in the other car parks in Meribel. You are obliged to come down to this one each night.
For UK campers. Note that Calor Gas freezes! Make sure you have non-freezing gas in your system as we get temperatures of up to minus 25c up here! Also put anti freeze in your Diesel. Local diesel is ok only to minus 15c. Also make sure you have anti freeze in your window washers for the same reason. Pull your wipers away from the screen at night or they will freeze to it.
Another good idea is to empty your water system totally on the way up as pipes may otherwise burst. Keep a supply of water in containers inside your camper instead.