They are usually some form of cotton and are wet cleanable. Just check for color fastness in a smal area and dont place them back inside the van until they are dry,because the cupboards they sit on are varnished which could mark them.
I could have had a vw free of charge in 2002, a great vehicle. In 1979 this old git around the corner from my parents bought a brand new T reg air cooled one, which was the last one made before going over to water cooled models. The miserable old timer only went on holiday in it once and on a weekly basis to his drinking club. When i used to come home from school, he would be sat in it with it's roof up.
When he died in 1990, a friend of my older brother asked him to make inquiries about it but my brother got in there first. Keeping it for about a year he then sold it to my other older brother who subsequently ran it into the ground. It was laid up for a while then offered to me for free. I wish i had had it now as he sold it to our cousin, who is rebuilding it from scratch. I bet this is one of the last made and low mileage.
Dave