From what I understand the A330's start flying in April from MAN-MCO but they will still fly the 747 on certain days.
Virgin will also start flying the A330's on one of the two daily LGW-MCO routes.
The A330's will not have any Upper seats for now.
The rumor's are they will be changing that but that has not been confirmed by Virgin.
So you could be on either. If you look at ''manage my booking'' on Virgin's website, if the seat map is availible, that will tell you which aircraft you are currently scheduled to fly on.