FR 1983 then FR 340 at Dublin
Biarritz → Dublin → London Luton
Timetable, Dublin time
17:20FR 1983 from Biarritz at the gate
14:40FR 340 to London Luton leaves the gate
21 h 20 apart on the timetable, overnight
FR 340 leaves 21 h 20 after FR 1983 arrives on the timetable: more than half a day, so not a connection we count.