Still don't know the reason for the delay, but the flight didn't leave MAN until about 2315, which would make it back into Cork probably about 4am ish. I'd of thought the CRK-Nantes would be better returning direct to Cork & another aircraft drafted to ops the MAN-Nantes return. I'm fairly certain by 2315 REA didn't have all the other 13/14 ATRs in the air.
The over-riding let down was being told at check in the flight would operate two hours late, when the aircraft was in fact still parked at Cork, which would = a 5 hour delay minimum.
Obviously OPS gave it their best shot but whatever plan they had, just didn't work on the day in question.