BA 349 then IB 718 at Heathrow
Nice → London → Madrid
Timetable, London time
21:05BA 349 from Nice at the gate
15:45IB 718 to Madrid leaves the gate
18 h 40 apart on the timetable, overnight
IB 718 leaves 18 h 40 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.