What factors led to some British Caribbean islands becoming independent and some remaining overseas territories? Why are places like Barbados and Grenada independent while places like Montserrat and Anguilla are still ruled by the UK?

Size as well as a lack of natural resources. Anguilla is a flat 16-mile-long island with little rainfall, that has around 16,000 people and limited natural resources. Anguilla also had to fight just to have a direct association with the British and so their timeline of independence is different. Montserrat has less than 6,000 people and a good portion of the island has been destroyed by a volcanic eruption.