LONDON — The debut teaming of two of the legit industry’s most venerable talents — composer Stephen Sondheim and director Trevor Nunn — may prove another lightning strike in a series of successes for London’s Menier Chocolate Factory.Nunn’s production of Sondheim and Hugh Wheeler’s 1973 waltz musical, “A Little Night Music,” which bowed at the 160-seat venue Dec. 3, has been largely well received by London critics, with rumblings of a West End and possible Broadway transfer starting to build. Save a few recent critical misfires (“They’re Playing Our Song,” “The Common Pursuit”), the Menier has turned into something of a hit factory since its opening five years ago. Currently represented in the West End by transfers of its productions “Maria Friedman — Rearranged” and “La Cage aux Folles,” the venue’s other notable hits include Sondheim’s “Sunday in the Park With George,” which moved to the West End and Broadway, picking up nine Tony nominations last season, and “Little Shop of Horrors,” which played the West End last year. The budget for “Night Music” is £420,000 ($620,000), making it the most expensive production in the Menier’s history, according to a.d. David Babani. A quarter of that budget is enhancement from New York-based production entity Baruch-Viertel-Routh-Frankel Group, which also paired with the Menier on the “Little Shop” transfer. The small scale of this staging — and its positive reception — are in stark contrast to Nunn’s most recent London outing, the $6 million tuner “Gone With the Wind,” a critical and commercial flop that closed in June after just 79 perfs. “Of course it’s hard getting back on the horse after you’ve taken a tumble,” Nunn tells Variety. “But you pick yourself up and dust yourself off.” The fact that the 68-year-old director of such musicals as “Cats,” “Les Miserables” and “Sunset Boulevard” has never staged a Sondheim show before is “not for want of trying,” he says. Repeated plans to direct various of the composer’s works, most recently a production of “Follies,” haven’t panned out; this staging of “Night Music” has been some six years in the planning, and at one point was envisioned as a major Broadway revival starring Glenn Close. After that and other large-scale plans fell through because of scheduling problems, Nunn decided to mount the show as a chamber piece — bringing the Chocolate Factory into the frame. Venue, composer and production came together in what Babani now calls a “dream ticket.” Many London critics agree, with raves coming from the Guardian, Evening Standard and Independent, among others. The most talked-about aspect of Nunn’s staging, however, is the casting of Hannah Waddingham (until now best known as the Lady of the Lake in the London and, subsequently, the Broadway production of “Monty Python’s Spamalot”) in the central role of fading actress Desiree Armfeldt. At 34, Waddingham is at least 15 years younger than the role is usually cast (the last time “Night Music” was seen in London, in a 1995 National Theater production, then-60-year-old Judi Dench played Desiree, winning an Olivier award). One of the Menier production’s minority of critical naysayers, the Daily Telegraph’s Charles Spencer argues that Waddingham is “far too fit, young and highly sexed … to catch the bittersweet melancholy of a character who feels her time is running out.” The effect of the show’s legendary 11 o’clock number, “Send in the Clowns,” is dulled, argues Variety‘s David Benedict, because Waddingham “looks as if she’s decades away from retirement” even as she sings of “losing my timing this late in my career.” Nunn, however, is robust in his defense of this re-visioning of the character, and indeed that crucial line reading from the song. “Desiree has just said she wants to stop acting, and only do it when she feels like it,” he explains. “People seem to think this line is ‘this late in my life.’ I was determined to cast the role so it would make sense of the story.” Regarding future plans for the production, which plays at the Menier through March 5, Nunn says, “Everybody involved with the show would like to see it go on and reach a wider audience.” The director underlines, however, that any transfer will retain the current scale. “Moving this show into a big musical house would be a death warrant,” he says. “For this chamber show, small is beautiful.” “Night Music” has been absent from Broadway since 1974, making it overdue for a return to the Rialto spotlight. The appetites of Gotham Sondheim fans likely will be whetted Jan. 12, when Roundabout Theater Company stages a benefit concert at Studio 54 of the show, with a starry cast headlined by Natasha Richardson, Vanessa Redgrave, Victor Garber, Christine Baranski and Laura Benanti.