It's probably been stated in other threads but of course Yorkston's chorus is a straight rip-off of Geoghegan's.

The first verse ends with the 2 lines
Fresh cockles and mussels alive, alive, o
Alive, O, alive O,
Chorus: Alive, alive O! I call as I go
Fresh cockles and mussels alive, alive O!

There are similarities in the tunes but of course this could simply be both authors imitating the actual street cry.