We had a lot of Liberal "Radicals" in the UK in the early 19th century who were like proto-Socialists. They sympathised with the Americans but arguably they were closer to the French revolutionaries i.e. less focussed on the freedom to make a ha'penny than universal suffrage.
The English had strong Radical movements like the Chartists but in Scotland we had so much conflict at the time between our large quantity of Radicals and the state that we call that period "the Radical War". A group actually planned to stage an uprising to establish a Scottish republic with our own printed money, but the British government infiltrated the movement with spies and the leaders were hanged and possibly beheaded.
For reference, I have a popular and highly quotable song that illustrates the very left wing attitudes of the time.
Is there for honest Poverty
That hings his head, an' a' that;
The coward slave-we pass him by,
We dare be poor for a' that!
For a' that, an' a' that.
Our toils obscure an' a' that,
The rank is but the guinea's stamp,
The Man's the gowd for a' that.
What though on hamely fare we dine,
Wear hoddin grey, an' a that;
Gie fools their silks, and knaves their wine;
A Man's a Man for a' that:
For a' that, and a' that,
Their tinsel show, an' a' that;
The honest man, tho' e'er sae poor,
Is king o' men for a' that.
Ye see yon birkie, ca'd a lord,
Wha struts, an' stares, an' a' that;
Tho' hundreds worship at his word,
He's but a coof for a' that:
For a' that, an' a' that,
His ribband, star, an' a' that:
The man o' independent mind
He looks an' laughs at a' that.
A prince can mak a belted knight,
A marquis, duke, an' a' that;
But an honest man's abon his might,
Gude faith, he maunna fa' that!
For a' that, an' a' that,
Their dignities an' a' that;
The pith o' sense, an' pride o' worth,
Are higher rank than a' that.
Then let us pray that come it may,
(As come it will for a' that,)
That Sense and Worth, o'er a' the earth,
Shall bear the gree, an' a' that.
For a' that, an' a' that,
It's coming yet for a' that,
That Man to Man, the world o'er,
Shall brothers be for a' that.