The INTERRED verse has been transferred from another song - an old rugby song called WORKING DOWN THE SEWER

CHORUS: Working down the sewer, shovelling manure
That's the way the soldier does his bit
You can hear the shovels ring with a ting-a-ling-a-ling
When you're working down the sewer with the gang

I have a full set of words somewhere - I'll post them if I find them.