FR 1453 then FR 340 at Dublin
Brussels → Dublin → London Luton
Timetable, Dublin time
18:15FR 1453 from Brussels at the gate
15:00FR 340 to London Luton leaves the gate
20 h 45 apart on the timetable, overnight
FR 340 leaves 20 h 45 after FR 1453 arrives on the timetable: more than half a day, so not a connection we count.