What is a film about a man who once ran a record shop in Northern Ireland doing opening a film festival in Eastern Europe? That was the question that was bothering me on my way to the 47^th edition of the Karlovy Vary International Film Festival. Are they such fans here of arcane punk trivia that a film dramatising the signing of The Undertones would be seen as positively mainstream? But when I finally saw it, I realised that this film by Glenn Leyburn and Lisa Barros D'Sa is actually a pretty good fit for a country that has had to navigate an exit from communism while resisting co-option by the west. Though it appears to be a biopic, Good Vibrations is actually a very buoyant and really quite infectious film about the power of hope as a force for change. It is also – quite crucially at a time when the coalition government is sidelining the young in far worse ways than Margaret Thatcher ever did – a very timely reminder of what a militant youth really stands for and can achieve together.

The reason it works is that Leyburn and Barros D'Sa don't hide from the raw reality of the times; Belfast was a war zone in the 70s, a once mixed city that had become ossified and partisan along religious lines. Into the no man's land in between – which, perhaps for the purposes of this story is apparently just a one-man land – steps Terri Hooley (Richard Dormer), a 60s rocker and music aficionado who spends £40 and, oh, remortgages his house to launch Belfast's first alternative record shop, the Good Vibrations of the title. The shop ticks over, and in the late 70s along comes punk, opening Hooley's one good eye (the other gets seen off in a short, school-days prologue) to the kids who don't want to know about The Troubles and just want to have a good time. Hooley jumps right in there, signing bands like Rudi, The Outkasts and... well, if you're under 30, you probably wouldn't have heard of them. But fame is not Terri's reasoning; instead, he's looking to find the future however he can, even if it's at the expense of his long-suffering wife.

The constraints of being a biopic do show, since the events of Hooley's life tend to make life difficult for the directors, who depict Hooley as a great champion of youth and yet have to deal with the irony of his inability to cope with being a father. There's also the self-aggrandising nature of his personality, and it's a testament to Richard Dormer's excellent performance (perhaps a BIFA nomination is heading his way?) that he makes Hooley sympathetic even as his friends are tearing their hair out over his selfishness and dreamy carelessness. Finally, there are some slightly clunky performances in the background, especially in a montage scene where Hooley goes to London and meets a succession of A&R men played by cast members who won't be troubling the Academy.

But these rough edges are, ultimately, to the film's benefit. It's not even The Commitments, never mind Fame, since this is not the usual rags to riches to rags again story that rock movies like to tell over and over again. Like all the best rock movies, Good Vibrations is about something else, which Leyburn and Barros D'Sa achieve deceptively well in a subplot involving Hooley's father, a failed left-wing politician. Though they seem worlds apart, they are only a lifetime apart, since both want the same things in life by different means. Though it dresses in leather, plays loud guitar and spills pints of snakebit on spit-and-sawdust dancefloors, this is a film about the right to unite and the start of one of the most breathtaking historical turnabouts in the late 20^th/early 21^st century. This is not to say that Terri Hooley began the peace process single handed but it might easily be ten years further down the line without him. And in the country where the term Velvet Revolution was coined, it seems only fitting that the film telling Hooley's story should begin its life here.