Fliegenmong
Presumably the QF 787 will be CatIIIC landing limits, so weather only a problem in a minority of flights.
Also many close alternates Lhr. From the initial approach heights a diversion to Gwk Stn Lut about the same fuel. All Cat III ILS
In my airline at Lhr with good actual weather and both rwys in use, with no ATC delays, we were allowed to plan the alternate side rwy a as our as the diversion, and commit when TOD.