Hi there
For Austria you only need to buy a single vignette. It costs about 8 Euro for 10 days. You can buy them at garages and services up to about 20 miles from the Austrian border. For Switzerland you have to buy two, one for the car and one for the 'van. They cost 40 Swiss francs each, and they must be bought at the border where the local police will stop and check you. I think you can also buy them in advance from the Swiss Tourist Office in London. the Swiss vignette last for a full year.
Happy Travels
BarryB