Space 1999 and/or UFO.
Both were, in truth, absolutely terrible, at least in terms of the writing/stories and the Godawful bad science. Not to mention some ropey performances from what were otherwise excellent actors (e.g. Martin Landau).
But they were damn good in terms of the set design/costumes/miniatures and the general aesthetics of them. Probably why some of those who worked on that side of it went on to do the same for Star Wars, and why they produced a large range of fondly-remembered childhood toys.
Only came in here because I was looking for the "dreams" thread, as last night had a particularly bizarre one where I was wandering around a series of interiors that were all decorated/furnished in the style of those two series*. Such a 1970s idea of what the future would look like.
[*Sadly, no appearance by Gabriel Drake]