Hi, I currently have a 2012 Audi A1 1.6tdi which has the rmc eu headunit without the double sd card slot (which is required for nav install). I have seen a headunit for the same year and model which has 2 slots and was hoping for some advice on doing a retrofit. I have some previous experience with coding cars (mostly bmw retrofits) and as far as I'm aware the headunit would need coding to the car? however I am unsure on whether the nav would then remain active or would need to be coded by an audi dealership (Would they even do it on a retrofit?). Another issue would be that because of my old HU I wouldn't have the Nav cable that plugs into the new HU, is this just an antenna? Has anybody done this retrofit or is it just not worth bothering?

If anyone has any knowledge it would be appreciated. 

Yep it'll need to be coded. You might find you need a different antenna. Might be worth you speaking to autologics or Audi retrofits to get more advice. Members have used both of these with success.