I'd recommend a diagnostic check to see if any fault codes flag up.
Also how old is the cars battery? I ask as a failing battery can cause cars to have various unusual electrical issues.
By the way you're English is fine 🙂
Can't believe this happened, and just highlights the importance of getting water ingress issues sorted asap for other members. So who footed the bill?
Was it your insurance company or Audi?
Bose would be easier to retrofit but I'd recommend you speak to autologics or Audi retrofits as members have used them for retrofits and been happy with the results.