Whilst it is certainly not an impossibility that NCL could see a service from QR I personally think EDI and BHX would be well ahead in the pecking order, EDI because it is the biggest UK airport without a Middle East connection and BHX because of its huge demand for ATQ and demand outstripping supply on the connections that are available (hence Mahan using 747s on their route from BHX to Tehran which connects to ATQ). I think it will be a long while before NCL sees QR and remember there also are a number of major European hubs not served by QR (DUS, CPH come to mind) that in terms of front end yield would come well above all NCL, BHX or EDI!