FlyingJ2K,
Today I also received the email you mentioned (my interview was last week). It specifically mentions the role of a domestic first officer as well, but I don't know if that rules out the 777 or not. The weird thing is, I have heard that Virgin has already contacted at least one of my references so why would they send me the e-mail afterwards??
It does say in the email that you have "progressed to the next stage of the recruitment process" so it definitely is a good sign!!