"Amazed to see it was in colour and good definition."
That is probably the 1967 Hammer film version. The original was a BBC TV series in 1958.
IIRC a BBC documentary*** showed how they did some of the latter's special effects: a path's gravel rippling under the fingers of a prone man (outside a vicarage?); electricity cables waving about wildly in the excavation site. Probably don't remember any other scary bits as I was hiding behind the sofa.
***Possibly a 2002 Timeshift programme "The Kneale Tapes"??
Biting the hand that feeds IT
