I'm fairly sure, when I first read it, I was as unaware of Lethbridge-Stewart's significance as viewers at the time were. It was only later I got things like The Making of Doctor Who and knew about UNIT. I must have seen some UNIT stories (I recall bits of Invasion of the Dinosaurs, for instance), but I think I was too young at the time to really appreciate the details of the plot. My first properly coherent memories of Doctor Who stories start around The Invisible Enemy.