Zam Salim is standing in the GFT foyer, looking a bit more proud than the average paying customer.

The poster for the Glasgow-based filmmaker's feature debut, Up There, is on the wall just to the right of the box office, sharing space with adverts for the re-release of Lawrence Of Arabia and It's A Wonderful Life. That's impressive and, in the case of the latter, appropriate company to keep, given Up There's quirky take on the afterlife.

The GFT is also an appropriate place for me to meet Salim, who came to Glasgow from Manchester in the early 1990s to study at university and has been settled in the city (apart from a short spell in London) ever since. It was here that Up There screened during the Glasgow Film Festival and here that I first came across what I'm convinced is one of the best British films of the year.

Set in a washed-out bureaucratic limbo where "carers" help the recently deceased to "sign on" until they're ready for the big move "up there", the story balances leftfield comedy and a melancholic tone that underpins each of the characters. Torchwood actor Burn Gorman delivers an unconventionally physical performance as Martin, the carer who arrives in a Scottish coastal town in search of a runaway soul. Channelling the spirit of Buster Keaton through the deadpan veneer of Jack Dee, Gorman provides the (un)beating heart of Up There's unique and peculiar mood.

"The concept was to make ordinary things strange," says Salim, "to constantly find the ironies, the absurdities, the humour in it. It's quite limited, actually, what you can do with dead people-"

In a way, the film's low budget has become one of its charms. With no special effects at the director's disposal, his characters can't pass through solid objects or turn the pages of the newspapers they read over the shoulders of the living. The physical comedy this generates is funny but, on an emotional level, we also feel the characters' frustration, their sense of being trapped. This scenario allows Salim to play around with myths and clichés about the afterlife.

"Why don't you fall through floors if you can walk through walls? "Why is there solidity under your feet but not in front of you?" he asks rhetorically. He adds: "I had a meeting in LA with one Hollywood producer who was interested in essentially remaking the film. But it became apparent after 10 minutes of conversation that he believed it was only for lack of budget that the film was what it was. With more money, he reckoned, the characters could have more superpowers. Which totally misses the point. He kept asking if I'd seen Ghost with Patrick Swayze-"

Meetings with Hollywood bigwigs are a far cry from Up There's origins in Salim's self-financed 2006 short film, Laid Off, which likened the dead-end process of being deceased to being unemployed. After it was promoted by YouTube, the short racked up half a million online hits, giving Salim some measure of audience currency to take to funders.

He and producer Annalise Davis have been rather savvy in terms of using the internet and social media platforms to create a ready-made audience for Up There's cinema release, most recently rewarding the fan who downloaded and most widely shared the trailer and movie clips with a red-carpet "People's Premiere" in their home town.

"It's a leap into the unknown using all the tools that are available," says Salim of the marketing strategy. "With an independent film, you can't hide your light under a bushel. We don't have a massive advertising campaign, we're not on the side of buses. You hope that word-of-mouth will spread but, because of the way this film is being distributed, you don't have time to build that up [when it's in cinemas] and so you have to be very upfront about it."

The result: Up There will open this week in cinemas from Falmouth to Inverness after its People's Premiere in Borehamwood, near Elstree; it's in contention for a Bafta in the best director and best film categories at next weekend's British Academy Scotland Awards and it has been named Best Independent Film at this year's Santa Barbara Film Festival in the US.

Not bad for a film that, to an extent, relocates Wings Of Desire to the seafront at Saltcoats. "I'd been looking at possible locations for ages while writing it," says Salim. "It just felt like you could make this film in Glasgow, and on the coast, because you wouldn't have to do too much messing about – the colours and the tones are already there. Someone at the Q&A in America asked how I made everything look so bleak. Well, this is the world we've got. And it's not bleak, it's just - consistent in tone."

Up There goes on release on November 16