Now admittedly SOF, my understanding of this is about third hand, but I understood that British Midland were doing very well at BFS thank you very much and had brought their first larger aircraft onto the BFS - LHR route, then had a ding-dong with BFS management about charges!? Don't think it was because anyone in Donington had a light-bulb moment and thought they needed to move those planes twenty miles down the road to an airport not ideally equipped to take them, but I could be wrong about that!??
The Belfast airportS thing is very unusual, even after all these years. Not all Heathrow passengers want to use City, same is likely true that not all Gatwick travellers would chose BFS. But leaving out the short journey issue between the two airports and leaving it to brand, schedules and, above all in Norn Irn, Price, it will be interesting to see how Belfast London traffic shapes up over the next while..