SATAN means weight off. At Heathrow this was known internally as 'wheels off' because 'wheels up' has a completely different meaning. Some departures leave wheels down for longer for cooling!
Asking for extra separation after line-up at a place like Heathrow is thoughtless and unprofessional, it causes disruption to the flow and interrupts the maximising of runway utilisation. At Heathrow departure times are predicted some time ahead and generally achieved until such thoughtless requests throw a spanner in the works. Crews requiring non-standard separation should inform GMP when starting, not once on a highly sought-after piece of concrete.