No need to kid ourselves: ‘Downton Abbey’ is less an actual movie than a special episode of the very British TV series that Yanks devoured like crumpets for six seasons from 2011 to 2016. Still, it’s fun to see the old gang again. As soon as John Lunn’s Emmy-crowned theme kicks in, the film version, written by franchise creator Julian Fellowes and directed by series vet Michael Engler, plays like old home week – unless you’ve never seen a single episode, in which case the script might as well be written in Sanskrit. Newbies will lose their way at every turn. The filmmakers have no intention of playing catch-up. A few things you need to know: The time is 1927, about two years after the series finale and the Crawley family and their servants are all atwitter about a royal visit.