I have recently viewed the 1958/59 six part series "Quatermass and The Pit" and have to say that despite the degraded monochrome picture it stands the test of time.
With this last installment of the Quatermass trilogy we get some insight as to how the BBC earned a reputation for cutting-edge science fiction in those dawn of the Space Age days, and well deserved it was to judge by this work.
The story differs in small detail from the later movie version (sometimes titled "Quatermass and the Pit", sometimes "Five Million Years to Earth") and the special effects are rather less impressive in a couple of places (but not so many as one might expect; the BBC splurged seventeen thousand five hundred pounds on this effort, a fortune in those days).
But it is the scope of the ideas aired that really make the production a winner. I'm quite well read in Golden Age through Cold War SF and I don't recall either of the two major ideas in this production being explored before (though I'm willing to be proven wrong). I'm not going to spoil here because the revelation of those ideas is a big part of the reason for watching in the first place.
Do yourself a favour and try and see this for yourself. I rather think the six-part show wins over the movie in a couple of areas, but the movie has obvious strong points where it supersedes the serial in quality so either version is a winner.
Do yourself a bigger favour and don't read the plot summary first.