In the 1970s and into the 1980s Aer Lingus 707s were used on a range of transatlantic schedules and charters, cargo services and some European IT charters such as to Athens, Rhodes, Heraklion and the Canaries, which were beyond the economical range of the 737-200 (other than a couple of the Advanced version acquired in the late 1970s). The fleet was wound down from the late 1970s and the last 707, EI-ASO, was in its latter years in all-economy configuration with I think 180 or more seats.
Remember that while the airline bought two 747s new, for a number of years one or other was leased out variously to Air Siam, BA, BCAL and (when a third was acquired) LAN Chile. Services were also operated by Aer Lingus 747s at different times in the 1980s on behalf of Kenya Airways and Air Jamaica. As noted, the 707s were leased out at different times to other carriers, including Zambia Airways, Libyan, Arkia, Transair Canada and Qantas. The airline also leased out 737-200s during the winter to a variety of exotic carriers. A complex story, far too long and detailed to recount here!