VickersVicount - you would think so, wouldn't you. But there is evidence that (for example) easyJet get higher yields out of Gatwick than Stansted, comparing like with like. Hence their willingness to pay much higher user charges at LGW than at STN. Looking at the ground origins/destinations of PIK's pax (based on CAA survey) a lot of them are from parts of Scotland that are a lot closer to GLA (or even EDI). It's perhaps not surprising that some of them might be prepared to pay a little more for a more convenient service. Or that pax who currently use other carriers might switch to FR if they were to operate out of GLA.
ATNotts - you may well be right. But if the price of giving the go-ahead to LHRR3 is a sop to the environmentalists then I wouldn't rule it out. And HAL has been making noises about the possible need for a congestion charge on cars in the Heathrow area. As well as addressing the environmental problems it might also be used as a way of funding the extremely expensive R3. Given that Davies seems to think that some form of public funding might be required for new runway capacity in the south-east, then all bets are off as to how this is achieved. A congestion charge on cars plus a restructured Heathrow-focussed APD might be one option.