There's a special treat for fans of indie rock at the Ultimate Picture Palace on Friday 15 August, as Alan McGee will be taking questions following the evening screening of the music comedy, Svengali. The founder of Creation Records and the manager of such bands as The Jesus and Mary Chain. Primal Scream, My Bloody Valentine, Oasis and The Libertines has a cameo in the film, which has been expanded from a popular online series.

Five decades ago, a Welshman called Owen wrote a screenplay about a day in the life of a pop group that became one of the most important British films of the 1960s. In transferring his popular web series to the big screen, Jonny Owen has not been able to replicate his namesake Alun's success with A Hard Day's Night and director John Hardwick is scarcely on a par with Richard Lester. But, while Svengali leaves much to be desired, it also has a conviction and an energy that enables this rattlebag of clichés and caricatures to amuse fitfully, while presenting almost no authentic insights into the workings of the modern music industry.

Postman Jonny Owen has always had an ear for music. So, he decides to leave his sleepy Welsh town and move to London with girlfriend Vicky McClure to find a band to manage to superstardom, as Brian Epstein did with The Beatles and Alan McGee did with Oasis. On arriving in the smoke, Owen heads for a garage on a tenement estate and uses a carrier bag full of beer to convince The Premature Congratulations that he is the man to guide them to the top. Once ensconced in a flat leased by crude Slavic landlady Katy Brand, Owen sets off in search of old school pal Roger Evans, who is now an A&R man with a major record label. However, Evans refuses to return Owen's calls and he is less than chuffed to see him when Owen doorsteps him and thrusts a C-90 cassette into his hand.

While Evans seeks sanctuary in Soho House, Owen pops into the premises of Irish shyster Michael Smiley to secure a payday loan to help him launch The Prems and keep him from raiding the wedding fund he has saved with McClure. The second Evans hits the pavement, however, Owen is waiting for him and aide Natasha O'Keeffe ticks him off for being so rude to an old friend. But Owen has the last laugh, as Evans drops his phone and Owen has tried every single contact in his address book (including an irate Bono, who is on an expedition to the rainforest with Sting) by the time they meet up for a pint. In the bar, they bump into Alan McGee, who likes the retro feel of the C-90 and gives Owen his card and an invitation to call him whenever he needs his advice.

A montage follows of Owen and McClure copying cassettes, sticking posters and handing out flyers in the hope of boosting The Prems on YouTube. Eventually, they get enough hits for Owen to assemble singer Dylan Edwards, guitarist Michael Socha, drummer Joel Fry and bassist Curtis Thompson in a downtown pub to break the news that they are going to play a legendary gig that will catapult them into the stratosphere. Edwards's interfering girlfriend, Nichola Burley, has misgivings. But she is shouted down, as champagne is ordered and Owen promises landlord Jordan Long that he will get hold of the £500 required to book the venue.

Realising that they need to get jobs to tide them over, McClure starts work in Iceland, while Owen replies to a want ad in the window of Mod Martin Freeman's record shop. He mocks Owen for wearing a tatty parka, but is browbeaten into taking him on because long-suffering wife Maxine Peake wants a holiday. Across London, however, Sorted Records honcho Morwenna Banks hears about The Prems and orders Mancunian sidekick Ciaran Griffiths to sign them up asap, just as rival Matt Berry warns Evans and O'Keeffe that they will pay with their jobs if they fail to clinch a deal.

As Owen pockets the wedding fund (without telling McClure) to meet his ever-increasing expenses, the screen splits to show him taking calls from a frantic Evans and technophobic mother Sharon Morgan back in Wales, who is concerned that father Brian Hibbard is unwell. McClure insists that they concentrate on the gig before heading home and Owen just arrives in time to intervene in a fight between Edwards and Socha. The latter accuses Burley of being the band's Yoko Ono and scarpers. But Owen follows him to a nearby floodlit football pitch and convinces him not to miss his shot at fame. Back at the pub, crowds are gathering in the street and the desperate Evans blags his way on to the guest list and ensures that McGee is barred. But barely a note is played before Socha and Edwards are at each other's throats on stage and a major punch-up breaks out.

As luck would have it, however, this seems to re-ignite the spirit of punk and The Prems are invited on to Sky's Soccer AM programme and given the chance to record a session at the BBC's legendary Maida Vale studios. The downside is that the band are now forced to sleep on the floor of Owen's flat, as they have been evicted from their own place and have nowhere else to go. Leaving McClure to cope with the noisy guests and their drunken entourage, Owen gets himself fired by Freeman before heading home. He is given a horseback ride to the door by neighbour Carwyn Glynn, while both parents and his brother-in-law slip him a few quid to tide him over. But Owen is distraught to learn that his father is dying and, as they sit on a mountain overlooking the village, Hibbard reminisces about his days as a teenage miner before giving Owen the wristwatch that has been handed down through the generations.

Hibbard also tells Owen to follow his dream and he returns to London feeling upbeat. However, he walks straight into Smiley, who takes the watch as a down payment on his debt, while he has no sooner stepped through the door before McClure orders The Prems to leave and she storms out back to her mother's after rollicking Owen for taking cash without asking. Trying to hold things together, Owen gets the band to the BBC and a slo-mo segment follows as they revel in the limelight and he sits in a corner and wonders what to do next. Skulking out of a celebratory party, Owen gets home to find that Brand has padlocked the flat and he has to kick the door down in order to recover his precious singles collection. Wandering the streets, he gets a call from O'Keeffe, who makes a half-hearted effort to seduce him before depositing him with Evans.

So relieved to have found Owen that he bales on a threesome, Evans tells him to cheer up and seize the opportunity opening up for him. He curses him for having a way with women and a knack for knowing a good band and urges him not to quit just to kiss and make up with McClure. The following morning, Evans sees The Prems on Soccer AM and realises they are going to be huge. Owen, meanwhile, has taken the five grand Evans gave him for his 45s and has paid off Smiley (without remembering to reclaim the watch). He is ready to go home, but McGee whisks him into the back seat of his car and tells him that Banks is turning the city upside down to offer him a mega deal.

Somewhat in a daze, Owen plays hardball with Banks and lands the biggest advance for a new band in UK music history. But, when he goes to the garage to tell his charges, he discovers that Edwards has quit because Burley has abandoned him for Socha and he has to take a train up to Scotland to coax him back south. Having convinced Edwards while sitting in canoes on a glorious loch, Owen gets arrested by British Transport Police for travelling without a ticket and he has to call McClure to come and pick him up. She drives up in her parents' car and Owen strives to convince her that everything will be fine if she just gives him one more chance.

Arriving in London, Owen rushes to the pub to tell The Prems they are going to be huge. But he finds Evans and O'Keeffe have beaten him to the punch. Thus, even though Edwards insists that nothing has been signed and is keen to hear what Owen has to say, he simply wishes them all the best and runs back to McClure and announces that they're going home

Never for a second managing to break from its webisodic structure, this has the feel of a picture that was made up as it went along. Owen cuts a genial figure as the Candide-like innocent abroad, while McClure proves a suitably feisty foil. But too many of the guest star cameos are strident or underwhelming, with Freeman struggling with some trendy quips about being a Mod, Banks spewing a slew of crude sexual references in a cod Scottish accent and Berry being reduced to ham up a litany of cartoonish threats to his underlings. Worst of all, however, is Alan McGee, who hides behind shades and beneath a Trilby hat (geddit) to deliver his dialogue with all the finesse of a six year-old reading a poem at a school assembly.

Editor Anthony Boys deserves credit for maintaining the pace and getting away with so many split-screen phone conversations, while no one can fault a soundtrack boasting cuts by Mott the Hoople, The Small Faces, Georgie Fame Dexys Midnight Runners, The Pogues, The Fall and The Stone Roses. Thus, while this is resolutely derivative, slipshod, self-satisfied and unfunny, it is no worse than Shane Meadows's similarly themed Le Donk & Scor-zay-zee (2009) or Sara Sugarman's Vinyl (2012).