Jill, here's the song you're after, performed by Berni himself! Betsy Loveless' Lament. I also had a strangely hard time finding it -- I found a second song of his about the Tolpuddle martyrs first, and that one directed me here. (I'll post that one in a second message).

Copied from the YouTube video description:

The story of the Tolpuddle Martyrs from the point of view of a wife left behind.

Adapted from the traditional song "Lady Keith's Lament"
LYRICS:

Here I sit in my lonely house,
Biting back tears that flow too often,
Thinking on those so far away,
Time has no power the blow to soften.
God is my strength and God my hope,
But God he doesn't bring in the wages.
Oh I shall sing such a joyous song,
That day my George comes over the water.

Friends we have and friends we've found,
Friends throughout the entire nation,
United we stand, divided we fall,
Heard on the lips of the whole population.
But friends can never heal the wounds,
Or end this pain of separation,
Oh we shall dance such a joyous dance,
That day our lads come over the water.

A curse on magistrates and squires,
On judges Whigs and ranting Tories.
A curse on those who obeyed their laws,
And left us nothing but hard luck stories.
A toast to those with banners red,
Whose cries were heard from here to Australia.
We'll join them in a rousing cheer,
That day our lads come over the water.

Working folk all over the world,
Whatever you win by negotiation,
They'll take away with a change of their laws,
Put you back in your place of degradation.
Remember on those Dorset lads,
Laws were only made to be broken,
We'll spite their laws and we'll celebrate,
That day our lads come over the water.