That is a very broad brush.
The British slavers opposed it.
The rest of the British then ended slavery.
William Wilberforce led the way.
Once he flipped the British government on the issue - by getting a stealth bill passed that allowed the British Navy to seize ‘neutral’ flagged ships. It was all over.
That broke the power of the slavers in parliment. The new parliments then strongly opposed and banned slavery. The British navy then implemented the policy.
Just as in the US, there were slavers and free people.
Is it your intent to say that William Wilberforce completely invalidates the work of Granville Sharp and Thomas Clarkson?
That is the result.
The problem with citing Br or Fr was they had no black people at all in their home countries, and the # of planters they were dealing with was miniscule, not 1/2 the physical country and 10% of the total pop.