I saw this when I was a child -- it was the first science fiction I'd ever seen (yes, even before Doctor Who or Star Trek). Being written by a famous astronomer, it was allowed to use hard-core SF concepts for a mainstream audience. A signal is received from outer space by Britain's biggest radio telescope and the country's largest computer is pressed into service to decode it. The laboratory assistant (played by Julie Christie in her debut role) is electrocuted by the computer, who uses her body as a template to create an android ambassador. [spoiler] At the end of the story the android flees across the Scottish wilderness and the last line of the story is delivered by the scientist who loved her: "We taught her everything... except how to swim."
Memorable stuff indeed - what a shame the original serial no longer exists.