I think that we should take a deeper look at their route structure. Currently they fly from LHR and LGW to EWR, JFK, BOS, MIA, MCO, ORD, LAX, SFO, LAS, IAD, JNB, NRT, HKG, CPT, and DEL. They also have 3 Carribean destinations that I do not know the codes for.
Now, many of these airports are served more than once a day. For instance EWR (Newark) has service from LHR and LGW in the form of a 747-400 and 747-200. I believe that JFK is served 3 times daily with a 747-400, and the 747-200, A340-300 switching on and off for the other two flights. HKG requires 2 airplanes to operate the route along with NRT. What I am trying to say is, that Virgin is playing with fire currently. I think they should hold on to the P&W "Classics" to allow some breathing room. Possibly, you could base 2 at LHR and 2 at LGW as back up aircraft. This would also lessen the stress of having to bring aircraft back from maintenance in shortest amount of time possible.
Any thoughts, questions or remarks are welcome towards this idea.
"History does not long entrust the care of freedom to the weak or timid." D. Eisenhower