Or consider routing the call over 1899 from your virgin line. 1p per minute to ROI landlines, all the time. Calls to ROI mobiles 15p per min all the time.
Or use 18185
Calls to ROI landlines 2p per minute
Calls to ROI mobiles 11p per minute
You can register with both carriers to get the best rates. You just dial a freephone access code from your virgin line, wait for the call to be answered then dial the full ROI number you require. Calls & charges listed through your online account within minutes of completing a call.