Frank Harte, in the first edition of his "Songs of Dublin" has the following as the (crucial) second verse of five:

And up to Rabbioti's together we did go
And the rapture there that filled our hearts, no poet e'er could know
We started eating one and ones and Mary softly sighed
"Oh I'd live for ever eating chips down by the Liffey side"

He also, BTW, has some minor differences in the George's Street verse.

I'd be loath to blame the Dubliners for your extra verse - I think they'd have made it scan!

Regards