I been on several factory tours of the Ingolstadt plant and always enjoyed them. I always find it fascinating how a modern car is put together. Perhaps I shall have to arrange a visit to the Brussels plant soon. Thanks for pointing out the videos.
I think you can book a tour of the Ingolstadt plant through Audi UK. You can also ask for a tour in with an English speaking guide and I think you pay when you are there. I assume the same would be possible for a tour of the Brussels plant.
You planning a trip wes, maybe jump on that wagon aswell.