I just came back from a vacation in the UK and bought a Right Connections trailer wiring harness for my GT. Ordered it with the 13-pin DIN trailer connector used on most of the newer European vehicles along with an adapter and a spare plug so I could make my own adapter to the US style, if needed. I have a UK cycle light board I plan to use with my bike rack to provide the stimulus to shut off the PDC in the rear and give the vehicle a little more visual impact when carrying the trike (I carry a recumbent trike in a basket behind the car).
But, finding a 40mm hole saw in the US isn't something you can get locally, and its delivery will delay my install for a bit. Hopefully, the thing's smarts will work with the US programming or it was a big waste. It may take awhile before I get it installed, but will update once it's in with my results.