FR 3976 then EI 158 at Dublin
Barcelona → Dublin → London Heathrow
Timetable, Dublin time
21:25FR 3976 from Barcelona at the gate
10:00EI 158 to London Heathrow leaves the gate
12 h 35 apart on the timetable, overnight
EI 158 leaves 12 h 35 after FR 3976 arrives on the timetable: more than half a day, so not a connection we count.