Ok, Derby Audi phoned a short while ago to deliver two lots of bad news and one piece of excellent news.
The fault is not covered by the warranty and the cost to me would be between £3k and £4k. Basically it needs a whole new glass roof and all components.
Fortunately, Audi HQ and the sales team at the dealer are going to split the cost between them so I don’t have to part with anything. One positive review coming up on Google once I have it back around the 19th