Hi, We have a 2004 X-Trail DCi SVE and I've just fitted a Witter detachable towbar with twin electrics to tow our 6-berth Bailey.
We've only used it once so far, but it did the job perfectly. There's room to fit an Alko hitch, and a bracket attached to the towbar structure provides for the electrics and somewhere to clip the breakaway cable (we didn't get that on the westfalia we had with our old car). Being detachable, we've found that it doesn't affect our rear parking sensors when it's detached and it also keeps the rear of the car looking neat and tidy.
We used TowEquipe for the towbar, we found them to be very helpful and knowledgeable and they have a very useful fitting helpline. If your fitting it yourself, I'd recommend the X-Trail wiring kit - it's good quality and simplifies the wiring process considerably.
If you want any more specific info, let me know !