Those places also have a huge wind resource in the form of the North Sea, for Ireland whatever the other bits of that submerged continental shelf are called, and for Poland the Baltic: https://globalwindatlas.info/en/

This is important because wind season anti-correlates with PV season.

Plus, it's not like north-south power lines are beyond the wit of mankind. The US western interconnection includes both Canada and Mexico: https://en.wikipedia.org/wiki/File:NERC-map-en.svg