How charming is Barnes? And how posh – even the flats above Londis have chandeliers.

Nothing but waves of goodness and gentility, then, as we find the OSO arts and performance space carved from the back side of an old postal building on the ducky edge of Barnes Pond. Bit odd that the theatre element should front the view and the adjacent restaurant face the side, but no matter – all shines with the burnish of volunteer enthusiasm and community spirit even if the toilets appear to have been repainted by somewhat trembly hands.

It’s buzzy, there’s generously-poured prosecco and an affable chap named Simon in a smart suit and John Smedley turtle neck introduces himself as one of the trustees. We appreciate his kindness, and the recently-fundraised £20,000 retractable seating system which makes this one of the more comfortable fringe venues in London.

It’s certainly a good idea to make a backstage comedy about a pop-up opera troupe putting on a show in a pub, and once the pop-up brigade has raided every opera in the repertoire, maybe they could cut and paste highlights from all of them to illustrate an original story. Equally, the notion that there might be a pecking order in the company, or older singers be jealous of young upstarts could be amusing if it weren’t also the entirety of the concept.

But this isn’t Noises Off for the Glyndebourne-going brigade. In Dress Rehearsal by AJ Evans, the cast clump awkwardly between the pub and dressing room halves of the set and a park bench on which some rambling backstory is played out mostly in mime and the staging is terrible. It’s hard to know whether the characters are deliberately clichéd and cardboard, or if it’s the acting and Paola Cuffolo‘s directing which are so shaky: surely it can’t be intentional to have Tony Baker as a fruity old tenor sing in a mellifluous style that was outmoded when Pavarotti was an errand-boy?

Two of the young singers have more interesting voices: Chiara Vinci is a promising soprano and at her most engaging when unaccompanied. Between bouts of his character’s tap-dancing flap-wristed overacting, Luke Farrugia could steer an interesting course between opera and musical theatre, although his contemporary Largo Al Factotum with Figaro shrieking ‘tag me or tweet me’ wasn’t half as clear as it could be. Duelling with her own piano, long-time Palm Court tinkler Karen Newby makes a striking contribution in a succession of backless gowns as the mute but meaningful pianist Phyllis.

It’s not enough to mash together snatches of Mozart, Bizet and Rossini with Gilbert and Sullivan and ‘I Sing The Body Electric’ unless the narrative also connects them, and preferably there are some laughs and fewer longueurs between cues. This dialogue could have been drafted by someone learning English as a second language, and is so banal and so trite you begin to play a game of ‘how many clichés can you get in one sentence’.  There is an informative and elegantly matte-printed programme: maybe get whoever wrote that to re-do the script?

For me, the high spot was The Mikado’s Three Little Maids – not because they did anything remarkable with it, but because the kimonos came from Susannah Cotton.  And boy, do I want one.