George Ridley (1835-1864; it was the last song he wrote) set his "Cushey Butterfield" specifically to the tune of Polly Perkins, which was well-known at the time from Harry Clifton's performances.

Clifton is generally credited as writer of Polly Perkins (though the tune shows signs of being based on another!) and the matter was gone into adequately in thread Cushie Butterfield: author?

There is no question but that Polly Perkins is the older song and that Ridley's was based on it. As you say, thread drift; except insofar as it disposes of a red herring.