The two aircraft you mention were G-VOYG (747-200) and G-VMIA (747-100). They were flown in by senior training staff, but I don't believe any unusual preparation was needed. The aircraft were extremely light, with (I think) all the interior furnishing stripped out. From my own experience at Kemble (in C130s), the runway's vertical deviations would cause more problems than its lack of length to a light 747!