Hi Tom
Thanks for posting your informative write up on your experiences with an imported car, interesting read and quite a lot of information I wasn't previously aware of.
In regards to the DAB radio, here is one you could consider from a UK company
https://www.iceboxauto.com/vw-passat-2013-17-gps-navi-android-11-carplay-oem-style-radio-vw105
Good luck with it all and please let us know how you get on