The
747 fleet that Virgin use on the Orlando run are actually newer than all but one of the LHR fleet.
The PE seats are not. The LGW seats are being replaced during the refits from May 2011.
One big advantage of their LGW 747s is that most of PE is upstairs in the "bubble".
As Paxboy says above check out v-flyer.com for trip reports. Some of these say that some people prefer the older PE seating!