It takes a while for this mess of an Irish comedy – or drama or musical or something – to spin off the rails, but, when it does, the careering vehicle will not be set back on course. Konrad Begg, an experienced TV director, delivers a decent-looking package with tolerably efficient performances. Unfortunately, the dog's dinner of a script ultimately proves beyond redemption.

Songs for Amy follows the sort of musician – all drearily sincere ballads strummed in acoustic torment – who really does clutter the streets of Galway. Sean (Sean Maguire) is in love with Amy (Lorna Anderson), a journalist, but, before they can tie the knot, he makes a classic rock star error.

On the night before the wedding, in the company of his band, he parties heartily with Alabama 3 and renders himself incapable of making the altar. Amy then runs off to New York and, for reasons never explained, falls in love with an unconvincing rock star whose malevolence could not be more conspicuous if he sprouted horns.

The first act plays well enough as an ersatz rural Once. The edifice really stars to judder when, after the springing of an unheralded tragedy, Sean finds himself running a luxury hotel in the country. Guess which celebrity couple are planning their wedding there? The team behind Mrs Brown's Boys would reject such a preposterous cliche. The longer the film goes on, the more palpable is the sense of desperation.

To be fair, everyone works hard at keeping the boat afloat. Begg frantically juggles the visual styles – faux-verite in New York; much sub-Tarantino slow motion for walking scenes – as the script spouts its unstoppable, clumsily constructed plot reversals.

We can, in a spirit of national solidarity, forgive most of this, but the hilariously pretentious dream sequence featuring an actual white horse really is too much to endure. Does Enya still need videos?