aHA - those missing verse halves? They were in Rise Up Singing, which I will paraphrase here:
Now when the bricks had fallen from the barrel to the floor
Sure, I then outweighed the barrel and I started down once more
Still clinging tightly to the rope, my body wracked with pain
And halfway up I met that bloody barrel once again!
The force of this collision, halfway up the office block
Caused multiple abrasions and a nasty state of shock
Still clinging tightly to the rope, I headed for the ground
And I fell among the broken bricks that were all scattered round.