I don't recall seeing this show as a kid, although I do have memories of owning a broken and battered Dinky UFO Interceptor toy. It was broadcast on the BBC a few years ago and I would have seen bits of it then, although not complete episodes.
Recently I bought the DVD box-sets and have been making my way through the early episodes.
The premise of the series is that Earth is under threat from aliens. A secret organisation called SHADO is set up to to combat the threat. There's an early-warning space station that alerts Moonbase, the first line of defence. If a UFO makes it past the Lunar interceptors and reaches Earth then other aircraft and ground vehicles respond.
Head of SHADO Ed Straker runs the secret organisation from a hidden base under a film studio and is played by Anderson regular Ed Bishop.
What is quite charming is that they've set the show in the far off futuristic year of... 1980! That's only a decade on from when the series was being made. In that time men have stopped wearing ties and lady astronauts have started wearing purple wigs. One nice detail they did get right was the use of cordless telephones.
Notable among the purple-haired ladies is Gabrielle Drake who plays lieutenant Gay Ellis. She would go on to appear in Crossroads among other things.
The show had fairly high production values and it's interesting to compare the quality of the colour images filmed on proper film stock with the grainy black and white Doctor Who episodes that survive from the same period. The makers also put some effort into the spacesuits and Lunar-surface sets for example.
