Humorist P.G. Wodehouse was quoted as saying ”In a Jeeves story, every line has to have entertainment value.” And this jaunty production is definitely eager to please. Built around Wodehouse’s treasured characters — the brat aristocrat Bertie Wooster and his immensely capable butler, Jeeves — this musical shoots us back to England between the wars (the old wars — I and II). The goal: to drum up interest in the romantic entanglements of several amiable morons from the upper classes. But under the direction of Alan Ayckbourn (who also wrote the book and lyrics), the show sputters from whimsical to wry to wearisome, sliding into a huge hilarity gap in its comic climax (Wooster mounts a ladder dressed as a pig). If the night has any significance, it’s that composer Andrew Lloyd Webber has left his lushness behind for a bright batch of jokey music-hall jingles. (In fact, the night’s most plush and operatic ballad is upstaged by a potted plant.) Like the rest of the play — and like Mamma Mia!, another new musical with a British pedigree — the songs define a space between the sincere and the synthetic. They shimmer with shallow affection. Some might be grateful for the easy emptiness of it all.