[Regulator]

As such, this means the 777-300ER with the new nacelles could operated out of London's Heathrow and Gatwick airports literally 24 hours a day with no restrictions

A good point. That would be an outstanding competitive advantage for them - the other guy's airplanes are prohibited from taking off while your airplanes are departing every thirty minutes!

[Paleo Conservative]

As such, this means the 777-300ER with the new nacelles could operated out of London's Heathrow and Gatwick airports literally 24 hours a day with no restrictions

As I recall this all got started with the proposed 747-400QLR program that was never launched. If the 747 Advanced is launched, this technology will will be incorporated into it. It would make no sense to continue building any previous 747 models, because the ability to operate at Heathrow or Gatwick at any time of day would affect the resale value of the aircraft.