The title, as I remember it from poetry at school (not my best subject!), is "The Destruction of Sennacherib", and it IS "cohorts", not "chariots" which were gleaming in purple and gold. I may be wrong in this, but I have a feeling that despite the title, Sennacherib was the destroyer, not the destroyed, so the title is a little ambiguous.

Although I am sure you could use a number of tunes, I think "Sweet Betsy From Pike" or "Ghost Riders in the Sky" are about the least unsuitable of those suggested; I don't think "My old man's a dustman", "British Grenadiers" or "Irish washerwoman" are so suitable, being too fast.