The ever customer focused crew up north have revised there refund policy
http://www.translink.co.uk/delayrepay.asp
If delayed by more than 119 minutes, not only do you get a 100% refund on a single ticket but you get the value of a return ticket for that journey
50% refund applies after only 29 minutes!!
Irish Rail of course don't want to talk about copying up north, I asked