BA 349 then BA 876 at Heathrow
Nice → London → Budapest
Timetable, London time
21:05BA 349 from Nice at the gate
15:55BA 876 to Budapest leaves the gate
18 h 50 apart on the timetable, overnight
BA 876 leaves 18 h 50 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.