Thanks guys - the Mudcat connection strikes again! Through another route I have found a version originally collected I'm told from a member of Pilgrim Morris:

This year I'm off to sunny Spain. With Rover, my spaniel.
I'm taking the Costa Brava plane. With Rover, my spaniel.
But, they won't let Rover on the plane. Not Rover, my spaniel.
So, we walked it all the way to Spain. My Spaniel's paws are sore.

I think the mention in the third verse of the original song that "every dog must have his lucky day" may have spawned this addition to the folk tradition - Cheers!