Why not get a smaller feeder airline in place, like Citywing with a 19 seater, flying into Stansted, Luton or Oxford? I incidentally messaged the Citywing facebook page and asked them about it, to them responding with -
''We currently have no plans to operate a Newquay service to London (though you are right, it'd have to be to Oxford, Stansted or Southampton as the destination). We have been watching what's been going on with FlyBe and Gatwick however, and I'm surprised that EasyJet aren't going to do it, considering we have a very similar situation here on the Isle of Man where they are going to continue the service.
We constantly evaluate new route opportunities however, and if nothing else does come off FlyBe and EasyJets movements, we may re-evaluate.''
Other feeders possibly Eastern with a J41, Loganair with a Saab340.