Great question! I think Google is going to be a great help in finding and comparing some different options for you. I ran a quick search for LTL freight shipping to northern Ireland and came up with a few promising options here. For example, it appears that FedEx offers freight servicing to Northern Ireland, here. It's worth calling them to inquire more.
If there is anything else I can help you with, please let me know.
Dirk | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog