As a 777 driver for BA I can assure you that the flap retraction schedule we use out of Sydney is exactly the same as anywhere else.
We accelerate at 1000' above ground level from V2+15 (approx) to 250knots.
We could be retracting earlier than other aircraft as we are carrying a relatively light fuel load for Singapore and so will reach 1000' sooner and accelerate better. Plus the climb gradient on a 2 engine aircraft is much better than a 4 engine one (because of engine failure considerations).
Hope this helps....
Rgds,
SR