That's funny, because it seems like the British have made a lot of really good movies about their colonial history. Ghandi, Lawrence of Arabia, A Passage to India, The Four Feathers, Zulu and Zulu Dawn, The English Patient, and Young Winston are a few of them. If you search "Opium War" on Amazon you will find many, many recent books in English about the subject, and I would wager than most of them are by Brits because they have a reputation for doing history well.

There is no way to teach about imperialism without gloating a little bit if it was your empire. Britain kicked a lot of ass militarily or manipulated natives with commerce to do their will. Often the people they were subduing had guns just like the British as that was who they had bought them from. If the people the redcoats were trying to conquer were warriors, they were in for a good fight, and if the situation required a machine gun, the British would manufacture a few, because they could.

A few British soldiers, missionaries, bureaucrats, merchants, and adventurers held whole nations in thrall. The mostly men that created the empire were bold and resourceful, and also pretty interesting in other ways. They studied the cultures, and recorded a lot about them since most were preliterate. They made the first maps of a lot of the places on Earth, and also did the first real science. They connected a lot of things together, because they were such great sailors.

The British ended the trans-Atlantic slave trade and stamped out slavery in Weat Africa. They built roads and railways, opened schools and hospitals, and established governments that weren't based on tribe. They drove the Germans out of Africa twice, and drove out the fascist Italians and put Haile Sailassie back on his throne. They helped to defeat the Japanese Empire in Asia, and don't kid yourself that they were any better than the Nazis. Of course they exploited the colonial subject peoples and ruled them as tyrants because they thought that they were the epitome of civilization, and maybe they were at the time. If you don't tell the whole story, it's a lie.

In any case, I'm sure that the present Prime Minister of the UK knows a little bit about British Imperialism, and how it has worked out fabulously for him.