I am so grateful for this thread!
I booked some flights for July with Virgin (direct) a month or so ago, and must have completely overlooked the fact that you can choose your seats online after booking, I just assumed it was like BA where you choose when you online checkin 24hours before.
I just went onto Virgin's website.. There were literally only a handful of unreserved seats left, luckily I managed to get two together!
So glad I read this, you guys saved me!