For a pre-2014 car you need the following:
- OEM tow bar (ebay.de)
- Button (ebay.de)
- "Trailer" ECU (p/n 4H0 907 383 C - ebay.de)
- Kufatec Loom
- Possibly an additional fuse strip if you want a full OEM install (Dealer)
- Bolts (Dealer)
The ECU sits between the boot and the rear seat bench to the left of the ski hatch, kufatec supply outline installation instructions with the loom.
I can help with coding if you need it, but be aware that the coding will get reset when it goes to the dealer - easily reset or you if you can get a friendly dealer to add "KF7 - Coding for trailer hitch" to the PR codes for your car.
Post-facelift have different part numbers for the ECU, need a different loom and installation instructions, but the actual towbar and button are the same. I have a post-facelift ECU in the garage