ABC had a series of interesting made for TV movies that were done in the 70's but rerun on alte night in the early 80's. One of them was remake or sequel involving Harry Palmer of Ipcress Files Fame. the other was a great scifi movie about an DEW(Distant Early Warning which was the title) station on the artic. The station was being invaded by aliens and the distant early warning was not a terrestrial attack but an extraterrestrial one. Of course it ended on a pessimistic sour note that the infiltration had succeeded.
There have been great cable tv movies as well as miniseries to vanish never to be seen again. Dawns Early Light, Through the Looking Glass.
Then the short miniseries almost movies like World War III