DRUK
I can confirm the above as announced today by HAL.
They could not explain where the new taxiways would be, or why they had not planned correctly beforehand. The cost of the appeal against the original decision which HAL won, falls to the residents of LB Hillingdon as wasted exercise. HAL believe the new taxi ways will change a noise footprint on the ground.
However not doing the work they wanted now saves them considerable money, as it would have to be removed in future for R3. Also if the easterly ops went ahead then a whole new set of residents would be greeted with a new overflying noise footprint on departures ie the NE corner of LHR.