There are some interesting details, about British capability and will to win the Revolutionary War, in a recent discussion thread in the American Historical Association group on LinkedIn.
It's clear that there are substantial economic and military considerations in any assessment of the relative value to the British of the North American colonies and the West Indies "sugar islands." As I've mentioned before, I infer from my reading that the British did not have enough troops and ships to simultaneously suppress the North American rebellion and also defend the sugar islands against French and Spanish predators. It seems to me that this suggests an interesting question: how hard did the British try to win the Revolutionary War?
I don't know the answer, but I'm working on learning more about the circumstances and expectations that shaped 18th century diplomacy and military initiatives by the British.
The Journal of the American Revolution looks like an interesting site.