BA 349 then BA 1402 at Heathrow
Nice → London → Belfast City
Timetable, London time
21:05BA 349 from Nice at the gate
15:20BA 1402 to Belfast City leaves the gate
18 h 15 apart on the timetable, overnight
BA 1402 leaves 18 h 15 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.