Is there evidence of an origin of Wild Rover Jack - we have several versions that bear little relation to the common one with all the indication that of it being a rural composition (thatch - barns etc.)

The thatch and barns are also what you'd expect a rural singer to add to an urban song to localize it. I noted Lanfiere's song from the 1680s as the antecedent here after seeing its incipit in the Bibliotheca Landesiana index; Malcolm Douglas dug out the full text and posted it. The familiar Wild Rover text has modified a few details and toned down the moralism, but adds no really new idea to Lanfiere's original and the verbal formulas are unchanged.

In Scottish tradition, The Hills o Gallowa is probably the best-known song generally believed "traditional" which has a known author. At one point there were a lot of Martin Parker's songs floating around in oral transmission, but probably not for 150 years now.