"Children of the Stones [with Gareth Thomas] is the revolutionary 1977 British children's television drama telling the story of an astrophysicist and his son who arrive in the village of Milbury to study the giant Neolithic stones which surround it, and the community which is held in a strange captivity by the psychic forces generated by the stones. [...] The show includes every 70s horror trope: ESP, telepathy, ley lines, ancient stones, wicca, the occult, the paranormal, the supernatural, astronomy, dance rituals, cults, black holes, archaeology, uncanny valley, creepy kids, a soundtrack that sounds like a Manhattan Transfer Halloween sound effects record accompanied by the obligatory theremin, and a bad painting alluding to dark secrets past, present, and future."
http://www.metafilter.com/157634/one-of-the-scariest-things-they-saw-as-children The entire thing (two and a half hours) is on YouTube.
https://www.youtube.com/watch?v=SwT0wLnT7Rc I've never hard of this one before, but it's exactly the sort of stuff I loved watching when I was a kid. Speaking of 70's horror, remember
Spectre, with
Robert Culp, 1977?