I am tired of promising lists set prior to 1900 dying out in the current List Thread. So I am starting out with two which are still not finished, but were started there.
Jacobite Britain
1745: Sir Watkin Williams-Wynn, 3rd Baronet (Tory) [1]
1748: Sir Watkin Williams-Wynn, 3rd Baronet (Tory) [2]
1750: Henry Scudamore, 3rd Duke of Beaufort (Tory) [3]
1754: Charles Wyndham, 2nd Earl of Egremont (Tory) [4]
1756: John Boyle, 5th Earl of Cork (Ultra Tory) [5]
1761: William Pitt (Whig with reliance on Patriot mobs) [6]
[1] The Jacobite rising of 1745 succedes, with Charles Edward Stuart being crowned as Charles III and the notable Jacobite Tory MP Sir Watkin Williams-Wynn being appointed Prime Minister.
[2] Williams-Wynn failed to put down Anglican and Presbyterian rebellions, and so sought aid from overseas, which resulted in Williams-Wynn and Charles III becoming little more than French puppets, complete with occupying army and military governor. Many rebels escape to the British colonies in America, who appoint a Viceroy in lieu of the Hanoverian monarch who has fled back to Germany.
[3] Williams-Wynn hands the leadership over to The Duke of Beaufort due to not being able to effectivly being able to control Protestant unrest and rumours of a Hanovarian plot among MPs and some of the anti-Jacobite Scottish clans. Beaufort tries to placate the growing tensions by attempting to reduce the growing French influence and negotiate with the increasingly unstable colonies. However, in doing so he comes up against Charles III and his suporters in the commons, the so-called "Ultra Tories" as well as those who acuse him of still being too close to the French and the Papists.
[4] Wyndham adopts a more conciliatory tone than his predecessor in his dealings with the king. Raises funds to put down spreading protests in Lancashire and Wessex by selling the Ohio Country to the French; a transfer of authority resisted (robustly) by settlers and exiles alike.
[5] The more "reliable" Earl of Cork is appointed Prime Minister to gurantee Britain's entry into the latest European War on the French side. However the entry onto the French side is deeply unpopular and there are rumours that the exiled Frederick Prince of Wales is planning to land an invasion force to reclaim the throne.
[6] Frederick lands an army raised in America, along with German mercenaries and Hanoverian/Prussian contributions, and marched across the nation. Despite military successes, Franco-Spanish troops maintained control over much of England, until the Patriots emerged. The Patriots were mobs that seized control of localities and set up committees in the name of 'True God and Britannia'. When the last Jacobites were destroyed in London, and the executions completed, a new Prime Minister was selected. William Pitt, a general in Frederick's army was chosen, but he had to rely on the support of the Patriot mob-committees to maintain peace and stability. Meanwhile, wealthy landowner, and favoured general, George Washington, was selected by Frederick to crush the last pockets of Jacobite resistance in the north and Scotland...
An Aborted American Revolution
1775: William Pitt (Whig) [1]
1780: Charles Watson-Wentworth, 2nd Marquess of Rockingham (Whig)
1786: Thomas Jefferson (American minority) [2]
1787: Charles Cornwallis, 2nd Earl Cornwallis (Tory) [3]
1790: Thomas Jefferson (American minority with support from the Whig party) [4]
1795: Charles Cornwallis, 1st Marquess Cornwallis (Tory) [4]
1801: William Pitt (Whig) [6]
1804: Jeremy Bentham (Radical-Whig coalition) [7]
1810: Jeremy Bentham (Radical) [8]
1814: Robert Jenkinson, 2nd Earl of Liverpool (Tory) [9]
1816: Robert Jenkinson, 2nd Earl of Liverpool (Tory) [Westminster Government
1816: Robert Owen (Radical) [Newcastle Government] [10]
1819: Robert Jenkinson, 2nd Earl of Liverpool (Tory) [11]
1824: Robert Jenkinson, 2nd Earl of Liverpool (Tory) [12]
1829: Robert Jenkinson, 2nd Earl of Liverpool (Tory) [13]
1835: Henry John Temple, 3rd Viscount Palmerston (Whig) [14]
1841: Henry John Temple, 3rd Viscount Palmerston (Whig)
1843: Robert Peel (Whig) [15]
tt entered a period of good health at the same time that Lord North was incapacitated by the flu. He negotiated an end to the American grievances, and integrated the colonies into Great Britain, so peers and MPs from Britain-in-America could take seats.
[2] Jefferson heads an unstable minority government after narrow splits within the Whigs and the Tories (largely over the issue of American over-representation in the Commons) leave the so-called 'American Party' as the largest coherent grouping in the House.
[3] After a vote of no-confidence after Thomas Jefferson unsuccessfully attempted to introduce American representation in the House of Lords, the Tories rode to a comfortable majority on a wave of contempt over the American delegation to the House of Commons. Lord Cornwallis, known for his harsh words against the colonies leads the country as First Lord of the Treasury and Chancellor of the Exchequer simultaneously from the House of Lords.
[4] Jefferson and his Americans form a new minority government with tacit support from the Whigs, with further reform and integration to the new transatlantic system being proposed.
[5] After five years in opposition, the Tories are returned to power after Frederick, the Prince Regent (OTL George IV having died in smallpox) agrees to call new elections.
[6] The American minority splits, as the southerners split from the northerners over the issue of slavery. The dynamic William Pitt (the Younger) fuses the Northern Americans into the Whigs, while the southerners join the Tories. Pitt create the Confederation system, whereby the American shires are split between three Confederations within Great Britain:New England, Middle, and South. These Confederations administer in the name of Parliament, and ensure the writ of law is applied fairly, this far from the metropolis of the realm.
[7] Jeremy Bentham and his "party of philosophers" consisting of Utilitarian philosophers had gotten into parliament in 1801. They made themselves well respected among Americans and Whigs for their command of rhetoric and their unapologetic determination to drive for reform. After having personally assured King Frederick I that he wouldn't touch the monarchy nor the House of Lords, Jeremy Bentham was duly appointed First Lord of the Treasury in 1806 after the elections that followed the death of William Pitt.
[8] Bentham earned considerable favour with the public through his reforms to constituency boundaries, extension of the franchise, and inaugurating equal rights for women. However, his attempts to abolish slavery and the death penalty did not go down well, and an ill-fated bill to decriminalise sodomy caused a crisis in the Lords. By 1813, Bentham's government was on its last legs...
[9] With Bentham's government collapsing in 1814, a election was held. The Tory Party, under the Lord Liverpool, gained power and swiftly planned to reverse the Radical Party's changes.
[10] The abolition of the (limited) female vote caused uproar amongst the chattering classes, particularly in Northern England and Scotland. Robert Owen, leader of the Radicals since Bentham's retirement, formed a Radical government in the North, pledged to bringing natural law and social equality for all.
[11] The British Army under the Westminster government swiftly crushes the rebellion in the north and the Radical Party is banned. Because of this Jenkinson grows evermore unpopular with working classes.
[12] Bizarrely, even as support for the Tories was dying out anywhere north of the Humber or South of the Firth, the Tories acquired a strong base of supporters in the American South. The issue of slavery becomes more important, and American issues increasingly appear on the agenda. The three Confederacies of Britain-in-America are increasingly seen as three new nations in the Union, alongside England, Wales, Scotland and Ireland.
[13] The Americans continue to be Jenkinson's lifeline as public unrest in Britain grows.
[14] The collapse of the Tory vote in much of Britain, and their concentration in the American South, along with the Whigs soaking up the Northern American and former Radical vote, sweeps Palmerston to power, promising to reform government, and enact an expansionist foreign policy. Unfortunately his promise to abolish slavery doesn't go down well in some areas...
[15] The American Secession began in 1842, caused by Palmerston's abolition of slavery. The Southern Shires unilaterally declared independence, and the United Shires of America was declared. The French, Spanish and Batavians consider intervening to wrest these colonies from Britain's hold. USA sympathisers assassinated Palmerston in 1843.