Well, an update on this. I took it to a VW specialist, who did a scan. He said there was nothing in the history to suggest a faulty camshaft variator, and that I should drive the car and see if the error comes back. He did say that it showed a failed o2 sensor, but the dealer never picked that up. As of today, the error has not returned. It was suggested to me that the dealer has a lot inexperienced staff who don’t know enough about diagnostics. I could have stumped up over 4K for nothing. That’s pretty scary. I wonder how many other people have paid for something that doesn’t need to be done...