If you have studied Horace Walpole's version, and you compare it with Child texts 75A & 75E, you must admit that those three represent a tradition that, above and beyond ballad vs burlesque, says "period piece." It is related to the other texts of LL but at the same time it is a separate tradition. 

Campbell: Hey down, hey down, hey derry, hey down, (ballad)

Walpole: Hey down, Hey down, Hey, hey dery down, (burlesque)

Percy: Dey down, dey down, dey down dery down, (two bit ballad do-over)

It should be noted that Campbell is an extremely reputable folklore collector. 75A & 75 E went into publication at the same time. So Percy's 75A "Northumbrian ballad" could never have influenced 75E. Of course, it could have "drifted" to the Wye, Kent spinners but somehow, I don't think so.

I think history has left a fairly straight trajectory. It began as a Jacobite ballad, a period piece, which became fodder for rabidly anti-Jacobite Horace Walpole's burlesque. He sent it to Percy and the rest is herstory.

I've read up on Percy & Campbell, and I've read Horace Walpole's letters. I know I'm right.