Yes, my Dad was well into Quatermass, too. I think he had seen it either on TV or in the cinema, and he certainly had some of the books. I remember reading this one (http://en.wikipedia.org/wiki/Quatermass_%28TV_serial%29) in my early teens.
And yes, your Mum's memory about the guy's face in The Quatermass Xperiment is pretty much correct. His skin goes kind of scaly and distorted as you can see reasonably well in this picture (http://www.digitalspy.co.uk/movies/i395095-8/hammer-horror-revisited-the-quatermass-xperiment-1955.html). Eventually, he turns into this (http://3.bp.blogspot.com/_WkKZJVG5wTk/S8AOXP-gchI/AAAAAAACg00/9oWzDe5L9-w/s1600/MovieQuiz_742-7.jpg)!
Re: Parents liking science fiction as much as we do!
And yes, your Mum's memory about the guy's face in The Quatermass Xperiment is pretty much correct. His skin goes kind of scaly and distorted as you can see reasonably well in this picture (http://www.digitalspy.co.uk/movies/i395095-8/hammer-horror-revisited-the-quatermass-xperiment-1955.html). Eventually, he turns into this (http://3.bp.blogspot.com/_WkKZJVG5wTk/S8AOXP-gchI/AAAAAAACg00/9oWzDe5L9-w/s1600/MovieQuiz_742-7.jpg)!