I'll let you know - I meant to have it done by now (had the kit for a month now!) but work has been crazy.
I bought the dedicated wiring kit from Umbra Rimorchi, the 7 pin type. It is a UK made product, I'll dig out the name if you need it.
If I remember correctly, the bar fitting itself is easy. It's the wiring up that gets a bit long-winded. You have to drill a 25mm hole in the spare wheel well to let the wiring pass though and the wiring has to plug into the tail light harnesses each side at the taillights, and also leads down the left side of the car tot he fuse box, where it again has to be plugged in.
What I do like about the dedicated wiring kit is that it is all plug and play. Being a new car, I don't want to mess with its wiring just yet...