I really enjoyed Quartermass and The Pit, the movie version.
I saw that as a child, and never forgot it. Really well done stuff.
Movie spooked me the first time I saw it. A good flick though.
The Quatermass Experiment looks very different. I’d never heard of this one. The Pit was a great movie.
https://www.imdb.com/title/tt0049646/
Quatermass and the Pit had another name too - “Five Million Miles to Earth”. It varied depending on the country of release.
https://www.imdb.com/title/tt0062168/
There are two Quatermass Experiment movies.
https://www.youtube.com/results?search_query=The+Quatermass+Experiment