It's a fascinating topic - I'm quite jealous of those students! - but do take what the songs say with a bucket of salt: it's definitely a case of "if the facts don't fit the legend, print the legend". (Lord Marlborough wasn't ennobled until after Charles II's time, never went to Newfoundland and died at home in bed.)

There's another, larger red flag which I'd hoist over the ballad sources in particular. A lot of the old songs aren't based on any history we know, but seem to be loaded with historical and geographical detail - there's the king of Eastermuir, the king of Westermuir and the king of Honorie, surely we should be able to place them on a map? we know the guy was knighted, we know his surname was something like Spens and we know what happened to him, surely we should be able to work out when? You can waste an awful lot of time like that.