Loffen, since you live in Norway some of the products suggested might be difficult to find. Here in Sweden, Lahega is a brand that many professional car reconditioners use ( http://www.lahega.se/ ). I don't know if any of Lahega's product are sold in Norway though.

The product sold under the Lahega name are meant for professionals, and are sold only in very large containers. Lahega also sell the same products under the Autorange name, meant for the amateur user, and in smaller containers.
I have used "Interior cleaner" with very good results http://www.lahega.se/showproduct.asp?id=670 . For example, the dash pad in my Corvair had been cleaned several times during the years I owned the car, with all kinds of products. It still looked a bit dirty though. After buying the above mentioned interior cleaner (to use in another car), I tried it on the Corvair dash, and to my surprise it took off a lot of old dirt that nothing else had taken off.

If you can't find Lahega's products i Norway, it might be a good idea to try to find a brand that the professional car reconditioners use. My experience is that they are much better than the normal do-it-yourself products.