There is a trick

Must originate from Dublin
Must be a EU/UK on mainline EI
Must be a EI issued revenue ticket
Must be ticketed before 5pm the day before travel
Frequent Flyer number with status must be the 1st named passenger and the number must be entered at time of making the reservation

Then check in after 9pm the night before (does NOT work for flights on 26th December)
Select the sit me anywhere option

100% success rate for me