Costumes, props, posters and archive footage all feature in an exhibition that leaves you itching to see some shows again Weave your way round the new exhibition Re:Imagining Musicals at the V&A in London, and you light on a fascinating contrast. Among the 100 objects on display are costumes, props, posters and a kaleidoscopic video of the 30 stage musicals recorded by the museum's archival department. But sharp-…