I did a bit of Googling and, after a few false trails and dead ends, I think that I've found the lost verse you were looking for.
And of all the words they've written, You will find that Les has far too few And the song should be much longer So he wants to add a verse or two It was Lennon and McCartney Who gave us a song that was filled with love And they did it in two verses In my life that's quite enough