Back in March I took a trip with Aer Lingus from LHR to DUB and back while visiting for work.
Aer Lingus mostly operate the A320 CEO & NEO in and out of LHR but on EI154 & EI155 they use the A321NEO LR.
I travelled on their Aerspace ticket which gets you extra luggage, lounge access and a seat in a business class seat. For £30 extra I thought it was worth it.
You will only get this seat if flying on a A321NEO LR so check when booking.
Enjoy the flight!