Hi they all do it not just Audis, when I was running Mondeos that was there favourite trick as well as spreading foam crumbs all over the carpet I used to go down the breakers and find a car that was picked clean and buy the passenger seat foam and use that as it had less wear, I think the new foam is probably your best bet and is easily fitted so that will be it for another 168k by which time I think you will be past caring LOL.
Steve.