Tigger, why wouldn't the current passengers using the U2 service to LTN not fly with the failing shamrock to LHR? 30 miles apart, yeah that'll just be a few minutes. Passengers fly into different airports for logistical reasons not just the price i.e. meetings and training maybe closer to STN than LGW, that is why they fly into STN.
Also, IMHO there will never be a 0600-0645 dep time for the EI to LHR. The other slots in use are worth far more to ROI rotations than north of the border, because if they were wouldn't there already be an earlier or same departure time for the midlands?
But sure, EI out of BFS to LHR should get out very quick considering there is very little traffic up at the lough this winter
How many tumbleweeds have went past you on the ramp?