The main participants told their stories years ago and there really is little or nothing left to tell.
I think that is a rather discouraging point of view. Black Buck took place around 28 years ago. The battle of Culloden, for example, took place 265 years ago yet people are still writing books about it. Imagine a historian having access to a soldier who fought in the battle who had previously not been asked to describe his experiences.
I know several tankers guys who flew on Black Buck who were not consulted when Vulcan 607 was being written. Not sure if they have anything earth-shattering to add, but it would good if they were given the chance while they are still around.