I have all the surviving Quatermass shows on DVD. The first series, The Quatermass Experiment, was made at a point when TV shows were broadcast live and could only be recorded by a crude method involving literally pointing a cine camera at a monitor. Only the first two episodes were saved as the quality was too poor - much of the second episode features an unplanned "alien monster" appearance due to an insect crawling across the cine camera lens. Quatermass II, Quatermass and the Pit, and the final story, titled simply Quatermass, have been released on DVD in Region 2 - I don't know about Region 1 or if they're available legally on any US streaming services.