We've recently returned from 2 months snowboarding in Switzerland, total expenditure on overnight parking was under £150, half of which was 2 nights in a campsite. It's not all good news though: your grocery bill will be at least double!
Here is a link to a Swiss motorhoming website with some useful stuff:
Bienvenue a tous les amateur d'une certaine liberte , quoi de neuf ? - Camping Car Club Suisse Romand vie et activites du club
We stayed in SW Switzerland (Vaud, Valais and Fribourg) so can only suggest a couple of place to stay. My advice would be to take some short cuts through the mountains rather than follow the motorways along the main valleys which can be quite urban and industrial.
After leaving Interlaken you will presumably go via Gstaad and over the Col de Mosses to Aigle. You can overnight at Les Mosses away from the road at the Arsat parking. If you dogleg a little further on there is a serviced aire at Leysin by the patinoire or non serviced in Les Diablerets at the sports hall. Down in the Rhone valley 10 miles east of Martigny there is free motorhome parking at the Bains de Saillon (and you can walk in to the luxury thermal baths facilities). There is another serviced aire at St Leonard next to the underground lake and up the "hill" above Sion there is one at Saviesse.
Almost forgot, before reaching Gstaad you could go north through Charmey (aire with servicepoint, nearby baths etc) and down to Gruyeres which is well worth a visit, especially if you are an "Alien" fan! Then on around to Les Mosses
The servicepoint in the Martigny motorway services was out of order but could dump toilet, the one further north outside the campsite at Villeneuve was working.
If you are using refillable gas don't bank on mylpg.eu being accurate, only 1 ou tof 5 stations in the area still had lpg and that was ths ENI station by the airfield at Sion. Probably the same across Switzerland. We bought a Vitogaz bottle for our visit, chf55 deposit but you get it all back when returning it; about chf46 per 11kg gas though. Available everywhere, 21.8lh hose fits.
Parking in large towns difficult, look out for a blue parking timer card (like blue badge timer) at a petrol station. You will need it if you want to park close to centres.
Feel free to ask questions
Kev
photo: SuperMoonRise at Les Mosses
