Peter-RB
Goodness gracious,
I never thought anyone in (or from)NZ would ever make sour comments like that about us "Good ole Brits"
By birth and upbringing, I'm a Brit too. I look back, with sadness and maybe a little bitterness, at the decline of Britain after WW II, and think of several reasons. One, of course, is the bankrupting of Britain by the war, the result of a conscious decision by Churchill (the right decision, by the way) and various actions by the US, a combination of anti-Imperialism and Anglophobia. Perhaps it was easier for Churchill to take a broad view of "the English-speaking peoples" because he was, after all, half American.
A dreadfully inadequate system of technical education, which made it very much second best to humanities subjects (I studied humanities myself, no sour grapes).
A very destructive rigidity in the class system, which explains both the poor standing of technical education, and the state of warfare that existed within industry a lot of the time.
Appallingly inept management. How did Britain lose a whole car industry?
Appallingly negative and destructive trades unionism.
A failure to come to terms with reality: in aviation, far too many prototypes and not enough concentration on getting one or two things right. And a hopeless desire to keep up with an imperial past, and an industrial pre-eminence that was gone by the second half of the nineteenth century. Why was France's aviation industry so successful, when Britain's struggled, at best?
In the face of all this, although it's certain that some members of the Parliamentary Labour Party were communist agents (as were, doubtless, some members of the Conservatives), you don't need conspiracy theories to explain the decline.