Whatever good came from British colonization was certainly not a result of British good will. They just ended up losing their colonies and left some structures that were useful to those who they had exploited to the max.
Imperialism is a historical force of civilization—like it or not. It has been that way from the dawn of history—starting with Sargon I to Egypt, China, Greece, Rome (one of the more successful empires) to others—England was one of the best. Yes, they exploit people but they do provide a peace, a system of trade and prosperity. Remember the Pax Britanica? Sargon and his family gave peace to the Middle East for 150 years (no small feat). Empires have spread ideas and beliefs—Do you think the Christian Church and message might have existed without a Roman Empire? We are in a time when the world is breaking into a patchwork of small states—most of them corrupt failures. Day will come when these will be gobbled up into new empires—We can only hope they will be led by the West rather than China or Japan. Want to read some sad history? See how China treated the lands they seized—like Tibet? Or how the Japanese treated the Koreans? Or the Turks treated the people they ruled? Imperialism will come again—Maybe this time Germany will rule (Third time is a charm they say) or a Greater Russia under Czar Putin.
Sure the Brits got some benefits for colonization, but in return they gave the fruits of a system that was 1500 years in the building (if you go back to the Anglo-Saxon moots that were the foundation of the British system). British colonies got the English legal and political system (which is pretty darned good, and forms the basis for ours - with variations) and the English religious/moral code (which isn't bad either).
Back when I spent a good deal of time in the Caribbean, the rule of thumb was that you could count on decent water, good roads, reasonably honest law enforcement, and an Anglican church wherever the Brits had been in charge.
And you can't compare the British Empire to some idealized concept of political perfection in your head. Compare it instead to its contemporaries: the brutal empires of Belgium and Germany, and the less brutal but wasteful & ineffective one of France (I once spent an hour trying to deal with a couple of Parisian customs officials who had been imported to St. Barthelemy. Even the locals hated their guts.)
What's really sad is that Britain seems to have given it all up with hardly a whimper.
‘Structures’ like the common law, parliamentary democracy and equality under the law.
The colonies that have adhered to these ‘structures’ are much better off than the ones who have torn them down.
Rhodesia has crumbled: South Africa is crumbling - precisely because they chose to tear down those structures.
But Canada and Australia are commodity powerhouses, India is a major industrial power and Jamaica is winning all the sprint medals - because they kept those structures.
You want to see "exploited to the max"? Check out the former "colonies" of the former USSR, like East Germany. In NO Brit colony did they ever have to erect a wall to keep people IN.
The Brits were pretty humane in how they conducted their colonies. You might say, they behaved in a Christian manner, turning a profit while keeping in mind the well-being of the people they ruled.