I have a feeling it might of been hellenic imperial airlines that sometimes operate for Lybian airlines or it might of been one of the many cargo (cathay Pacific, Jett8, Great Wall, Air China) 747s you might of seen (pls correct if wrong).
I was in work around that time of night on monday and i think it was the Hellenic aircraft, but i was some distance away!!!!!! who knows!! hope that helps a little.........anyone with more info please feel free to correct me as im not certain im right anyway!
cheers and good evening.