Celtic FC also use "Fields of Athenry", which makes it a bit of problem in some quarters in scotland (i.e. if around any Rangers fans!

Ipswich Town also had "Keep Right on to the End of the Road" back in the 60s when Alf Ramsey was manager (before he went on to be England's World Cup manager). As far as I know, it's no longer their song. Never a folk song: it was written by Harry Lauder, after the death of his son in WW1 see:
http://en.wikipedia.org/wiki/Harry_Lauder
and listen here: http://www.youtube.com/watch?v=fgqhdpPB8Y4