Thanks. Yes it's obvious one song seems to be derived from the other.
I just found this page: https://mainlynorfolk.info/steeleye.span/songs/theupsanddowns.html where it mentions "Chris Willett sang As I Was Going to Salisbury in 1962 on the Willett Family's album The Roving Journeymen."
I listened to that (incomplete) version, it's similar to verses 2,3 & 4 of the version I posted and has the same tune. It's a closer match than the Steeleye Span version.