If you are a high time pilot looking to do a conversion, and you have over 500 hours on multi pilot airplanes, then you should be looking for somewhere where you can do your 14 exams and find a simulator in Europe of the same airplane in which you are type rated. Lots of guys have been going to Bristol Groundschool for these types of conversions for the theory. There are also some other choices around.
As far as NAC, I would stay away.