Spotted this and thought someone might find it of interest;
Megabus usually do a £1 deal on random dates for random locations, and don't advertise them, but if you do a bit of hunting you can usually spot them.
If you select Rosslare to London for 23rd - 28th April, it's just £2 return. Trip is between ferry and bus and is about 12 hours so won't be for everyone, but even if you got there or back one way and took a plane return I imagine it would be saving a good deal of money if you happened to be traveling around those dates! There are more to other destinations but usually takes a bit of hunting to find them. Hope this is of help!