Coming this week from England to Apple TV+, "Still Up" is a romantic comedy about a pair of London insomniacs who keep in touch through the night by smartphone and laptop. Its underlying construction, that of friends who are possibly destined to be something more, is not new. "When Harry Met Sally ..." springs readily to mind, and with protagonists who never share physical space, it's a chip off of "Sleepless in Seattle," not to mention the sleeplessness.