Grand Central's website has just been updated (about time too - its "News" page has had a message saying it WILL start services on 18th Dec for weeks now).
"We were hoping to introduce our full timetable of services this month, but unfortunately this will not now be possible because of further delays in the delivery or commissioning of vehicles from the organisations undertaking their refurbishment.
Frustratingly for all of us, these delays mean that we cannot at this stage accurately predict when we will have enough reliable rolling stock to introduce the full timetable.
Whilst we currently have two train sets in working condition, we still have no back-up vehicles delivered, or available, should anything go wrong, and we cannot entertain introducing further services until that position improves.
We have been looking at the possibility of hiring-in, on a short term basis, other trains capable of the required top speed of 125mph, though that is not an easy task."
I guess its frank enough