You will not see this advertised on their site but I got an email about the deal after booking a cheap deal between Liverpool and Belfast. Dublin is also available too.
Book by 31 January for travel between 1 Feb and18 Dec.
We book an overnight return journey from Liverpool to Belfast around St Patricks Day in March. For 119 pounds we got complimentary evening meals and breakfast and an en suite family berth for us and the two kids.