I know you have, and no it doesn't. The idea that the ARW was a trigger for British abolitionism is revisionist history pure and simple...
I'm
almost tempted to say this doesn't deserve a serious answer since it seems to pretend that "revisionism" is somehow alien to the formation of common historical narratives (it isn't), but is a practice to be avoided at all costs by "respectable" historians. Revisionism simply is the reinterpretation of orthodox view, nothing more nothing less -- and it is essentially to the discipline and study of history. Now, with that out of the way...
The idea that the ARW was a key factor in the successful organizing of British Abolitionism is actually not that controversial when one looks at the debate in full -- in
Moral Capital: Foundations of British Abolitionism, Christopher Leslie Brown identifies (correctly, I think) two major schools of thought as to why the British Empire came to ban the Slave Trade in 1807, one about moral progress pushed by abolitionists, the other about the economics of Empire. The latter has its roots in the descendants of British Caribbean slaves re-examing the trade's end in the 20th Century; Eric Williams'
Capitalism and Slavery (1944) in particular makes the case that it was economics that doomed the slave trade, and that abolitionists only "
campaigned against the slave trade and slavery when it became economically convenient to do so" (Brown's paraphrasing). And the key event to this shift in the underlying economic reality, Williams said, was the loss of the North American colonies.
The other, older narrative has its origins in the first history of the movement, written in 1808 by none other than one of its most prominent leaders, Thomas Clarkson; focusing on the moral character of the British abolitionists and the British nation, it essentially made the case that the "
moral arc of the universe [or at least Britain]
bends toward justice", a sentiment that would be expressed by future abolitionists (and eventually Dr Martin Luther King). However, even Clarkson admitted that the success of the American Revolution played a vital role in the organizing in his movement, saying twenty years before he wrote his history, "
As long as America was ours, there was no chance that a minister would have attended to the groans of the sons and daughters of Africa, however he might feel for their distress".
Brown seeks to look at other psychological motives for the abolitionists and their supporters, connecting the movement and its success to changing views on empire and nation, themselves brought on by (all together now) the success of the American Revolution. But whichever narrative we go with, the role of the America's Independence cannot be denied -- if we go with moral progress, then Britain's loss was necessary for her to seek redemption; if we go with economics, then the imperial economy must first take the hit of said loss; if we go with a change of political consciousness, then we need the previous one to be in crisis.
The fact remains that before anti-slavery sentiment in Britain organized itself into a movement in 1787, it was only that -- sentiment -- and posed no serious threat whatsoever to the vast slave interests in the Empire. To the idea that abolitionism was a
trigger for the ARW, well -- the preceding sentence alone would destroy any pretense of taking it seriously, to say nothing of the fact that the Revolution began in Massachusetts (where slavery was far from essential to the economy), or that the Declaration originally laid the slave trade at the feet of the British Crown, or really the lack of any evidence whatsoever (save the odd letter of James Madison, written in the midst of the war, to some tory leaning plantation owners).
Anyways, with that out of my system, I suppose I'll comment on the OP: I'm just going to say that having the Americans lose the Revolution anytime before the start of the Southern Theater (so, say Saratoga flipped) is going to be a big help. Conservatively, I can see the Atlantic Slave Trade continuing as usual for another quarter of a century; if you want ideas on making that last longer... well sorry, don't have anything right now.
The British navy were already actively hunting down slaving ships by this time.
Citation needed.