I wasn't suggesting that the possibility of a NetJets engineering base at SEN has anything to do with "the choice of destination that the punter wants to fly to." They may simply be looking for an engineering base in the London area and would position aircraft to and from there. That would make sense surely.
By the way, I believe that NetJets do operate revenue sectors out of SEN at the moment so I don't believe that it being outside controlled airspace would be necessarily a negative factor.