For me it was UFO (Gerry Anderson). For some reason I was given a UFO annual in about 1975. It may have been a 1975 annual, but why there would be one I don't know as the series was shown in 1970.
Same here! UFO was great, still enjoy watching that from time to time, it's one of those rare old SciFi productions that are still very watchable today.
That, and a german scifi kids book called "Schiffbruch in der Erde", which is about a Professor who built a ship that can travel through solid earth. To me, the whole concept of having a base of sorts was immensely fascinating as a kid. Now I have a house with a selfmade home automation and alarm system, and my house computer voice is Xerces from System Shock 2, so in a sense I got my wish