Pip,
A bit of background to THE MEETING AT PETERLOO.
It came from a newspaper contemporary to the event which I found in Labour historian Eddie Frow's personal library in 1968 while researching local songs.
Unless there is another version, your text seems to have undergone several changes; the 'With Henry Hunt we'll go' chorus comes from another song which only partially survived and was on the Critics Group album 'Waterloo-Peterloo'
'Meeting' was included in Sam Richards' and Tish Stubbs' The English Folksinger (Collins 1979)
The text as I got it was:

1. Come lend an ear of pity while I my tale do tell.
It happened at Manchester a place you know right well.
For to redress our wants and woes reformers took their ways.
A lawful meeting being called upon a certain day.

The sixteenth day of August eighteen hundred and nineteen
There many thousand people on every road were seen
From Stockport, Oldham, Ashton and from other places too,
It was the largest meeting that reformers ever knew.

Brave Hunt he was appointed that day to take the chair.
At one-o-clock he did arrive, our shouts did rend the air.
Some females fair in white and green close by the hustings stood
And little did we all expect to see such scenes of blood.

Scarcely had Hunt begun to speak: Be firm, he said, My friends.
But little still did we expect what was to be the end
For around us all so hard and cruel regardless of our woes
Our enemies surrounded us on the plains of Peterloo.

The soldiers came unto the ground and thousands tumbled down
And many armless females lay bleeding on the ground.
No time for flight was gave to us, still every road we fled.
There were such heaps were trampled down, some wounded and some dead.

Brave Hunt was then arrested and several others too.
They marched us to the New Bailey, believe me it is true
And numbers there was wounded and many there was slain
Which makes the friends of those dear souls so loudly to complain.

Oh God above look down on those for Thou art just and true
And those that can no mercy show thy vengeance is their due.
Now quit this hateful mournful scene, look forward with this hope
That every murderer in this land may swing upon a rope.

But soon reform shall spread around for sand with the tide won't stay.
May all the filth that's in the land right soon be washed away.
And may sweet harmony from hence in this our land be found
May we with plenty all be blessed in all the country round.

Jim Carroll