Even in the years of painfully limited production budgets, British television produced sci-fi programs that achieved cult status in their homeland and abroad. The many incarnations of “Doctor Who” are probably the most familiar example. In 2006 the Doctor delivered a popular spin-off, “Torchwood,” concerning an institute grappling with extraterrestrial encounters. The musical composer for recent “Doctor Who” iterations, Ben Foster, was handed the job of writing the “Torchwood” score. His soundtrack recording, Torchwood: Childrenof Earth, has just been released on Silva Screen Records. Performed by the BBC National Orchestra of Wales, the music combines wonder and unease, brooding moments with flights of heart-pounding anxiety and passages of hopeful calm that dart like rays of sun on a gloomy British day in keeping with the story’s mood.