BA 1489 then BA 15 at Heathrow
Glasgow → London → Sydney
Timetable, London time
21:30BA 1489 from Glasgow at the gate
21:00BA 15 to Sydney leaves the gate
23 h 30 apart on the timetable, overnight
BA 15 leaves 23 h 30 after BA 1489 arrives on the timetable: more than half a day, so not a connection we count.