Britain had a dictatorship during both World Wars. This is not a slur, not hyperbole, it is a fact. Normal business was suspended, emergency measures taken, rights sacrosanct during normal times no longer enjoyed protection.
Neither is there some ‘contradiction’ between a country favouring democratic institutions during peacetime and periodically installing a dictatorship in times of trouble. This is the nature of countries where there is a constitution. It is what happened in Rome during the Republican period.
In monarchical-type countries or absolutist regimes there never are dictatorships because (if they are truly monarchical or absolutist) there is no constitution and no suspension of the constitution.
Concentration of power in the hands of few men, the British cabinet, facilitated Britain’s wartime performance. It didn’t mean they won both wars because of this – France used a similar tactic and was defeated in World War II – but it was a necessary step and the US did the same.
With respect to WWII, it is strange that Britain and the US claimed to be fighting dictatorships while they were existing as dictatorships at the time. But it is a fact and it would have been foolish of them to act otherwise.