On the Google Voice webpage, towards the upper right-hand part of the page, you'll see a CALL AS (your GV #) and below that, an input fields that has a type-over of ENTER A NAME OR NUMBER. Enter the telephone number of your correspondent. You will get additional prompts to where GV should call YOU and then after you answer that call, it will connect you to your correspondent.
[I noticed that the CallCentric rate to Ireland is quite cheap. Maybe it is a problem with Brexit? ;-) ]