Who in Australia would know more about Sweet Charity than Nancye Hayes?  She won her way into the hearts of the theatre-going public 40 years ago, playing the soft-hearted, eternally put-upon Charity Hope Valentine in the original J.C. Williamson production of the classic musical.     Now she brings her inside knowledge to bear as director, hitting all the right buttons to make The Production Company's first show of the year a dazzling success.     Sweet Charity reworks a Fellini movie about a hapless waifish prostitute, turning her into a dance hall hostess at the tawdry Fandango Ballroom in New York, where men pay just to dance with girls.     Songs such as Hey, Big Spender (as the girls greet their clients), The Rhythm of Life, I'm a Brass Band and There's Gotta Be Something Better Than This helped establish it as one of the definitive musicals of the 1960s.     The show rests squarely on the shoulders of the singer/dancer who plays Charity -- in this case, pocket dynamo Sharon Millerchip, a leading lady with a rare ability to put onlookers in thrall.     Nimble and effervescent, this impish gamine toys with her audience, bending it to her will.  When Charity sings and dances If My Friends Could See Me Now to celebrate meeting a famous movie actor, Millerchip radiates the glee of a kid let loose in a toy emporium and it's impossible not to be gleeful too.     Underpinned by a first-class band directed by John Foreman, which gives just the right edge to Cy Coleman's jazzy music, and new choreography by Ross Coleman, it is a polished, stylish and thoroughly entertaining show that no lover of musical theatre should miss.     Hayes proves unerring on the comedy, pointing every laugh in the vintage Neil Simon script.     She does not put a foot wrong, and therefore neither does her cast, which is particularly well chosen, notably Matt Hetherington, whose characterisation of the gormless tax accountant Oscar Lindquist, on whom Charity pins her hopes, is wonderfully well sustained, Alan Fletcher as seriously suave Vittorio Vidal, the Latin lover, and Louise Bell and Kirsten King as Charity's rough but warm-hearted buddies at the Fandango.