Probably can’t be seen if you are not in the Uk but the BBC iplayer has Quatermass and the Pit, it’s the old 6 part black and white tv series first shown in 1959 and it well worth a watch if you can see it.
I have never heard of this show until you mentioned this, looks like you can get it on DVD for like $8 on Amazon. And doing a little digging they also have like a remake of a series called ‘The Quatermass Experiment’. I believe if you have Amazon Prime you can watch both of these.
The tv series Quatermass and the pit was remade as a film by Hammer in the mid 1960s and it was known in the US as Five Million Years to Earth. you can find the Tv series on YouTube but the quality not that good.