I was at Newark Air Museum on Saturday for the Vulcan's display. The place was completely overwhelmed with visitors, they hadn't expected quite so many people. The cockpit was open, but they had had to have a list and on this occasion I couldn't get to see it. They occasionally also fire up the Auxiliary Power Unit, sadly they don't fire up the main engines anymore.
Given the crowds at Newark, I would suggest planning ahead if you want to go to see XH558 flying.