I'd be a small bit surprised.
Where the ATR wins out is where it can support several daily services when the A320 would only have one. So, it's an ideal fit for ORK-BHX, but for DUB-BHX, where there are already 3 A320 flights, it would only make sense if someone had identified a market for 6+ flights a day.
There's also the question of where Aer Arann could find a suitable aircraft to dedicate to that level of service.