"Shanwick Control" has two 'Clearance Delivery' frequencies, 123.95 and 127.65, staffed by ATSAs (Assistants) at the Prestwick OACC, for the issue of Oceanic Clearances to westbound flights about to enter Shanwick. As BOAC states, they cover only as far south as LASNO and ETIKI. (On a good day!)
"Shanwick Radio" has two 'HF Assignment' frequencies, 127.9 and 124.175, staffed by Shannon Aeradio Officers at the Ballygirreen Radio Station, for the allocation of HF primary and secondary frequencies to westbound flights about to enter Shanwick , but they also extend only as far south as LASNO.