Andy - I'm having a similar problem as you but flights are even worse from Glasgow. I have a deadline on the Friday and so can't take a half day and need to get an evening flight.
There is an Aer Fungus flight from Glasgow-> Dublin departing about 9.30pm on the Friday and one from Edinburgh-> Dublin about 8.30. Both about £60 return but miss last Limerick train. Can hire a car for about £60 at Dublin Airport and drive to Limerick. Total cost of £120 + petrol but obviously economies of scale if more than one in the car (and savings on train tickets).
It's all a bit of a hassle but I don't have many other options (other than Glasgow->London-> Shannon which costs a fortune). If you want to save half a day's holiday and the later flight + car interests you then email me.
I may need to go back on the Sunday night which causes other problems. Will cross that bridge later. .. There is a ridiculous early flight from Dublin on the Monday morning which would enable just half a day off work, but would mean no alcohol for driver and possible need to skip bed altogether on the Sunday. Don't fancy an afternoon at work after that, although I might get away with the "working at home" trick if I keep my phone on and make up the time later
Anyone know the venue yet?