Hi Will,
When you mention a NI address I'm assuming you use "Parcel Motel" ??
There's a new service from An Post that will bring parcels from a mainland UK address to your local post office
€3.50 for up to 20kg 
https://addresspal.anpost.ie/
HTH
John
Thanks John, I'm aware of the new An Post service. It looks good but don't exceed the weight/size limit as its then €25 (Max 20kg and size less than 72cm X 31cm X 25cm)
My comment was more about the Royal Mail and or the suppliers involved.
Why do some suppliers not want the export business?
In Irelaand the Homebrew shops (Nort and South) will deliver any where up to 30Kgs, next day usually for just €6 using DPD or Nightline!