Actually the sudden fight for independence was quite a while after WW2 when you still had an impressive military. Fighting for places like India (now a super-power) and Rhodesia (then a rich country) also Iraq (good oil amrite) would mean that The British Empire would be one of the most powerful nations in the world.
This statment seems plucked out of fantasy. After the second world war the British military, industry and economy was severally weakened. For example, before WW2 all other world wide currenices were measured against the British sterling, due to the devaluing of it during the war, and the following Bretton Woods Accord we lost a major economic advanatge on the world stage.
Further more, our industry had been bombed up and down the country over the years by constant german bombing runs until the Battle of Britian was won. This required major resources and a lot of time to get it back onto track.
Although we may of still held a decent standing military, influences from around the world way beyond mearly a count of military units influenced the fall of the british empire and its inability to hold onto its territories. India itself fell after some poor management decisions and actions, for example the Amritsar Massacre.
Controlled territories is not quite as simple as having military power. While we had guns and the people we oppressed did not it was simple. When everyone has guns, then its not so clear cut.