The version quoted at the site Brakn linked to is the same as the one in John Brophy and Eric Partridge, eds., Songs and Slang of the British Soldier: 1914-1918, 2nd ed. (Eric Partridge Ltd. At the Scholartis Press, 1930, pp. 72-73):

THE OLD BARBED WIRE
   Air: ?

If you want to find the sergeant,
I know where he is, I know where he is.
If you want to find the sergeant,
I know where he is,
He's lying on the canteen floor.
I've seen him, I've seen him,
Lying on the canteen floor,
I've seen him,
Lying on the canteen floor.

If you want to find the quarter-bloke,
I know where he is, I know where he is.
If you want to find the quarter-bloke,
I know where he is,
He's miles and miles behind the line.
I've seen him, I've seen him,
Miles and miles behind the line,
I've seen him,
Miles and miles and miles behind the line.

If you want to find the sergeant-major
I know where he is, I know where he is.
If you want to find the sergeant-major,
I know where he is,
He's boozing up the privates' rum.
I've seen him, I've seen him,
Boozing up the privates' rum,
I've seen him,
Boozing up the privates' rum.

If you want to find the C.O.,
I know where he is, I know where he is.
If you want to find the C.O.,
I know where he is,
He's down in the deep dug-outs.
I've seen him, I've seen him,
Down in the deep dug-outs
I've seen him,
Down in the deep dug-outs.

If you want to find the old battalion,
I know where they are, I know where they are.
If you want to find the old battalion,
I know where they are,
They're hanging on the old barbed wire.
I've seen 'em, I've seen 'em,
Hanging on the old barbed wire,
I've seen 'em,
Hanging on the old barbed wire.


Note: A significant variant in the last stanza was your sweetheart for the old battalion, with the corresponding grammatical changes.

The "snippet" also at the site is what is on The Great War CD: "If You Want to Find the Sergeant Major... (trad.) -- The Roosters Concert Party (Rec. 1929. Mat. WA 9050 (part); Regal G 9369)," with this note:

Sung here in the style of "Seaside Follies", this sounds a cheery, jokey refrain. Other versions, which range from the C.O. down through the ranks, end with the haunting verse, "If you want to find the Private, I know where he is, he's hanging on the old barbed wire". Some variants place "the old battalion" itself in the fearful situation, but every version expresses the private soldier's belief that ultimately he is the one that will pay the price that war demands.

~Masato