The Aileron used for the premiere is #250, this one was later converted to the Aileron Spyder. So it's the same car with the same VIN.
#251 is indeed a testcar. She has a Ruby / Ivory bi-color interior. This testcar was first used by Lotus in England and later by Spyker themselves in the Netherlands. This one was spotted twice I think.
I checked and you are absolutely right: No pictures yet in the #251 thread
Would you be so kind...