There are two main ways to get to the chalet, either flying or driving.
If you decide to drive down, we can suggest a route that avoids around 1/2 of the motorway. Having driven this route many times, it is just as quick as the motorway but a shorter distance avoiding some of the motorway tolls. There are many places that are suitable for a overnight stay with a drive time in France of around 8.5 to 9.5 hours.
There are flights from Heathrow to Geneva all year round and many other regional airports during the ski season. Other airports serving this region include Chambery and Lyon.
Either book a hire car at the airport (NOTE: Hire on the Swiss side of the airport as you get winter tyres included or you will be charged a crazy amount at the airport and it takes longer. The French side will be a few Euros cheaper but its not worth it) or take one of the plentiful shuttle busses that will bring you up to the valley. Many of these will drop you at the door of the Chalet with prior arrangement.