Thanks to Simon V for this update:
Virgin's check-in desk and baggage handling is now on the A side of the main terminal, the opposite to where they have always operated in the past. They actually have more check-in space here, so it should be a better situation for those waiting in line at the Virgin desks. However, this does mean there is a change in the arrival process. Virgin will STILL use the arrival gates at Airside 3 (Gates 60-99), which goes against established OIA practice (airlines using Landside A are supposed to operate from Airside 1 or 4, Gates 1-29 and 100-129), BUT, because the only international arrivals terminal is Airside 3, Virgin will continue to arrive at their normal gates but then direct people to Airside A (Level 2) to retrieve their baggage, NOT Airside B as in the past.
It will certainly cause confusion for Virgin regulars who will automatically assume they still need to go to baggage retrieval on Airside B when they arrive. Virgin say they will have plenty of staff to direct arriving passengers to the new baggage retrieval on Airside A, but it may catch some people out.
The bottom line is Virgin was getting increasingly cramped for check-in space on Airside B, and, with their extra summer flights likely to kick in soon, they have found this compromise to try to give passengers a better check-in service. It's not ideal, but hopefully it will work better for dpearting passengers.
This change has been implemented as of this week, so it will affect all Virgin flights henceforth. And, for check-in, you need Airside A, not B.