I think that the program makers were foolish to compare certain public sector workers' salaries with that of the PM. The PM's salary is effectively just a token gesture or stipend if your prefer. It doesn't really represent the amount of responsibility that the PM accepts.
Neither did the comparisons take into account all the other things that the PM receives for free from the public purse such as accommodation (No.10 and Chequers), free travel to and from anywhere in the world, free... just about anything you care to mention whilst he's in office. Not to mention the enormous amount of money that most PM's can expect to make once their tenure is over.
The bottom line is that some people are worth every penny of their salaries and some people are grossly overpaid. It's simplistic and wrong to use a broad brush and state, for example, that no head teacher should be paid more that X amount per year. If that head teacher is outperforming his peers and turning failing schools into successful schools, thereby giving a chance and hope to students who would have otherwise had none, I think it's churlish and disingenuous to limit his salary in such an arbitrary way.