Just had another thought.....how long does it take for A380 to get from "fully ready" (I hated typing that!) to being at the holding point ready for departure?
5? 10 minutes? That's not a lot of notice to get the inbounds set up for an RNAV and/or increased spacing inserted into the sequence. Gatwick tower seem to do an amazing job at anticipating where the gap needs to be but how much notice can realistically be given to the inbound?