There was a thread here somewhere - where someone had replaced the plastic covered wheel - from memory it was easy and quite cheap.
Have a search throught the threads - you may be lucky.
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That thread is in the projects section
Thanks for that link. I got one of K&D and took off some thickness with the grinder. Put it all together again and it seems to work.
So window is fixed and today the automatic gear box of my Volvo broke down.
It never ends.
Matt