There are many variants of the tune: almost every single one of John Mehlberg's recordings is slightly different but they are all basically the same tune. Maggie May or Darling Nellie Gray or Keep Your Feet Still Geordie Hinny (usually just the first half of the tune) are as close as you need to get. MAGGIMAY in DT is too slow; NELLGRAY is more like the tempo it's usually sung at.