FR 3801 then FR 7808 at Barcelona
Birmingham (UK) → Barcelona → London Luton
Timetable, Barcelona time
15:35FR 3801 from Birmingham (UK) at the gate
12:45FR 7808 to London Luton leaves the gate
21 h 10 apart on the timetable, overnight
FR 7808 leaves 21 h 10 after FR 3801 arrives on the timetable: more than half a day, so not a connection we count.