Martin very kindly corrected the errors in transcription I had made.
Full lyrics for anyone else interested:

JACK'S SONG (by Martin Curtis)

Long before sunrise, we're out of the sack
Throw tea and flour in your battered old pack
Hang all your traps round your trusty old hack,
Away to the brown hills of Pisa

We eat rabbit curry, we eat rabbit stew
We've tried rabbit roasted, and rabbit pie too
Without us there wouldn't be one single ewe,
Up in the brown hills of Pisa

CHORUS: And it's gut 'em and skin 'em, and five for a bob
Some people say it's not much of a job
But give me my freedom, just me and me cob
Up in the brown hills of Pisa

A rabbit has never done me any harm
His meat kept me fed and his fur kept me warm
He gave me my living, he earned me my farm,
Under the brown hills of Pisa

We catch 'em by trapping, we kill 'em with shot,
We'll send down a ferret and bring up the lot
But now it's 1080 and leave them to rot,
Up in the brown hills of Pisa

CHORUS

The rabbiter's life was the life that I knew
A horse and my traps and my old 22
But *myx is the next thing they're going to use,
Up in the brown hills of Pisa
* myxomatosis

CHORUS