On the other hand there was some popular middle class and working class opposition to imperialism. William Morris organised large protests calling for Troops Out of Omdurman during the Gordon invasion. Radicals openly supported the cause of the Boers in the fight against British imperialism (as did Lenin). James Larkin rallied support for the strikers in the Dublin lockout among British workers. British socialists organised a Hands of Russia campaign blacking ships carrying troops to Archangel, and on Lenin's advice re-directed their efforts to a Hands of Ireland campaign. Glasgow engineers organised a strike wave undermining the British effort in the First World War (and see Ken Weller's Don't Be A Soldier, for more on North London's opposition to the war). East Enders elected the radical Socialist supporter of Indian independence Shapurji Saklatvala to parliament. Soldiers and Labour party members exposed Britain's war against the Greek resistance fighters.
Of course, all of this I am listing here is the parallel history, of the opposition that did not win the day. The mainstream of official Labour Movement politics has been pro-imperialist. The office holders and MPs always identified with Britain against her enemies and recalcitrant subject peoples. Still, it would be a mistake to assume that the Labour leaders imperial policy had the positive support of their members. Rather it was a case of the working class accepting that it had no say on matters of high politics, surrendering foreign policy matters to the "experts", while being restricted to the 'bread-and-butter' issues of pay, hours and conditions of work.
"There are complexities re Africa -- but no one in England or the U.S. or France did anything to stop Leopold. And France continued his ravishing of Africa even after the overthrow of N.III and the establishment of democracy. France even bears some responsibility for Rwanda I believe. And so forth. One _can_ say that 20th-c bourgeois democracy was better than 195h-c -- but I don't know if that really helps."