The two running prototypes that were used as show cars were built by RML (Ray Mallock) who has a long history in motorsport. I read an article about them in Autocar and the level of attention to detail (both engineering and to interior trim fit and finish) was extremely high for cars that were initially conceived as a simple marketing exercise to bring the standard car greater exposure. No doubt the fact they were so well engineered and able to be tested on track and at speed by journalists has made the decision to produce them in limited numbers much easier for Nissan.

I'm guessing the "production" versions will also be built by RML and not the factory in Sunderland.

http://www.topgear.com/uk/car-news/nissan-juke-r-driven-2011-01-17