If Flybe offered the canx pax the choice to reroute them via DUB then the airline is responsible for the onward taxi/coach to BHD
2nd scenario -
If it was the pax who suggested to Flybe that there are seats on the DUB, can we get on it...
I think then Flybe could say we will not pay for onward transport BUT the EU261 clearly states that the airline must reroute pax as quickly as possible by any means/route/airline/mode to get them to their destination promptly - So a reroute via DUB is quicker than Hotac at LCY and then a new flight the next morning...So BE still should pay the bill
Either way Flybe should be looking after its pax...