I expect you're right and some clever composer has made up this tune for the advert. It's just that it stirs something in my old head, and I'm nearly sure I've heard it many years ago. The last two notes of each line used to have two firm beats of a drum (boom boom) It's so familiar, but I'll have to let it go.
Teddy Bear, again, is similar but not exactly right Michael.
When/if I get to heaven, I'll tackle the crumpets and Old Speckled Hen first, then God will say, "By the way, Eliza, you know that song that drove you mad? Well, it's ..."
Thank you so much for taking the time to reply everyone. Much appreciated.