I've had the opposite experience with Virgin Atlantic. Tried to book upgrades into Prem Econ or Upper Class on Syd-Hk-Lon return for end of April/May - NO AWARD SEATS available within a two week block! And now I can't get the points back from Virgin (transferred from Amex) to try and use with...
Virgin are no better than the other airlines. Blanket unavailability of award seats in the weeks surrounding holidays, despite there being seats available. They're all the same!
Transferred Amex points to Virgin Atlantic to use as an upgrade and now told none available within a week either side of our travel dates. Only transferred because was assured by VA on phone that upgrade at least to Prem Econ would not be a problem. Didn't make a booking at that time though...