Arthur C. Clarke tries to see what he can see of those mysteries that border respectability. He's not trying to turn away from science but to give those vague borderline mysteries a chance. He tries to see what's possible. He even tries to criticize the standard respectable explanation of Stonehenge; that it is a solar observatory(at least in this episode). In the end, these video's serve as the rationalists responce to the fears and superstitions of mankind.
Here, he finds some stuff that maybe non-England living people wouldn't know about. I know of some stone circles in Sandinavia and Carl Sagan in his "Cosmos" video's shows a beautiful Native American Indian "stonehenge."
The question that seems to me to come up is why did these people stop progressing? I think they stopped exploring. Religion took over and everybody just kept coming to their stonehenges over and over again; they never learned anything new - for thousands of years till the Romans stomped them out.