So what do you do next after you've made the most successful British comedy film ever?

Three years ago, film producer Christopher Young was asking himself that question. At the time he was revelling in the money machine that was The Inbetweeners Movie, the big-screen spin-off of the scurrilous, scatological, often screamingly funny sitcom he'd produced for Channel 4. The film spent the rest of 2011 breaking box office records. It's now stands in the Top 20 of the most successful British films ever made.

Does such success bring pressure? A little, Young tells me as he sits in his office on Skye. "Having been responsible for The Inbetweeners series, I have been very conscious that the only thing people want from me since then is more of the Inbetweeners," he admits.

But success is also a currency you can spend as you choose, and Young has chosen to spend it the Highlands and Islands. So what do you do next after you've made the most successful British comedy film ever? Why, you make a new three-part contemporary drama on Skye. And you make it in Gaelic. Obvious, really.

When Bannan airs on BBC Alba in September, it will be the first original drama on the station since it began in 2008. Another five episodes of the series have already been commissioned. But before either reaches the small screen, the series will get its world premiere at the Edinburgh International Film Festival next week.

That in itself tells you something about how film and television are perceived these days, and how TV is changing. "What's happening in television is people are wanting it to be more cinematic," says Young. And Bannan is, he hopes, just that. Despite a limited budget it's been filmed on high-spec to make the most of the Skye landscape. "I said to [Film Festival director] Chris Fujiwara that TV is the new film," Young adds, "which is a bit of a cliche. The long form - whether it's Homeland or The Killing or Breaking Bad - has become the medium of choice for many talented people in the States or Denmark or elsewhere. Suddenly everyone's saying TV's just as good as or better than film."

Time will tell if Bannan can join that list. It's a family drama (Bannan means family ties) and in the current post-Killing, post-Borgen TV world we live in, its producer hopes the subtitles won't be as much of a hindrance as they might have been even a few years ago. In short, he's hoping the programme can gain an audience beyond the Gaeltacht. "It is set on an island, but there's nothing in terms of the lives of these people that doesn't strongly overlap with anyone's experience of living in Scotland currently. I think it will appeal to not just Gaelic people but to Scots, because it's a depiction of our own lives.

"We chose to set some of the scenes in the city because we didn't want it to be exclusively rural. And the reality of rural life in Scotland is we spend a lot of time going backwards and forwards to the city. We didn't want to do something that was nostalgic and, I suppose, pastoral, when that's not true to everyday life. Many people like myself in the Highlands spend half their time in Aberdeen, Edinburgh, Glasgow, wherever. And, equally, I think a lot of folk living in Edinburgh, Glasgow and the rest spend a portion of their time heading up to the Highlands and Islands. We do have in Scotland quite a singular experience of life perhaps. We mix the urban with the outdoors in lots of ways, and it's quite normal."

What isn't necessarily normal is the idea of a Gaelic drama in the first place. They're not exactly common. Try to name one, and the only one that comes to mind is STV's Machair. Bannan, then, is ploughing fresh ground. Young is proud of two things about the series. Firstly, it's not a genre piece. "Most TV executives will say, 'What we're really looking for is something like The Line Of Duty', and the truth is what they really mean by that is they want something that's good and popular. And the things that tend to be good often tend to be one-offs. With The Inbetweeners we didn't sit around saying, 'What are we going to make this like?'"

And, he points out, when he was making The Inbetweeners as a sitcom, it was just a low-budget project in line with other things he'd made, such as the film Venus Peter. In that sense Bannan is more of the same: a new idea made on a limited budget and with fresh faces. "I would say 80% of our cast and crew are first-timers on Bannan," Young points out.

In his way, then, he's trying to address the talent drain that flows south, whether south is Glasgow or London. "Talent is probably not getting enough changes to express itself in Scotland. There's just not enough going on here. What happens is the more people go away, the less stuff is made here. So you've got to reverse that somehow. Unless you create opportunities for people, nothing's ever going to happen here."

One of the first-timers taking her opportunity in Bannan is Debbie Mackay who plays Marie, one of the programme's central characters, a city lawyer who's returning to the island of her birth for the first time in eight years. Mackay, 28, knows that story herself. Based in Inverness, she's had to answer the familiar question that faces the young in the Highlands and Islands. The question of staying or going. She left - to go to university in Glasgow at 18 - but after time in London and Drumnadrochit, she returned to work at the Eden Court Theatre. Bannan is her first onscreen role.

Perhaps it was inevitable really, I suggest, given that the writer happens to be her aunt. "No, not at all," she laughs. "She was actually part of the auditioning process and obviously, not wanting to sound biased, she was saying absolutely nothing. And so it might have worked the other way." And anyway, she says, one of the auditions involved a kissing scene. "So this audition was with a man I'd never met, with my auntie sat in the corner. Just a wee bit bizarre. That certainly wasn't helpful to me."

What Mackay likes about Bannan is its contemporaniety. There's no romanticising of Highland and Island life here. Or not much. "Because we filmed on Skye, and Skye is absolutely beautiful, I don't feel you can get away from the romanticism of the place. But hopefully the storyline will be a bit more contemporary and people will be able to identify with the storyline. A lot of folk think the Highlands is just about peat and tweed, but it's not. There's a lot going on. People have the same issues, regardless of where they are in the world. The emotional issues hit everybody."

With a mother from Lewis and a father from Inverness, Mackay grew up speaking both Gaelic and English. She'd always wanted to be an actress, but the idea of Gaelic acting was a non-starter for so long. "When I was in school Machair was all we had and that faded out and there's not really been anything since. So acting in Gaelic wasn't really an option."

She's hoping Bannan may begin to reverse that. In the meantime she's directing a youth theatre show in Ullapool and worrying what she'll wear to the Edinburgh International Film Festival screening. "I need to consult in case I turn up in my frock and everyone else turns up in jeans."

Young is rather more familiar with the festival experience. His first job after leaving school was working for the Film Festival back when Lynda Miles was the director and the likes of Martin Scorsese, Wim Wenders and Woody Allen would make their way to Scotland. His abiding memory is of a "very glamorous party at the Edinburgh Commonwealth Pool where everyone jumped in, which to an 18-year-old seemed very decadent".

"Lynda definitely presided over a very heady festival time. It seems to be what Chris is trying to do now; mix the popular with the arthouse, the unexpected with the expected. Inviting a three-part TV show that's in Gaelic to premiere in Edinburgh is very bold and it shows that he's prepared to break boundaries."

Young will also be represented at the festival by The Invisible Life, a Portuguese film directed by Vitor Goncalves, which, he suggests, shows "the breadth of Edinburgh". It goes without saying that it also shows his own range. He met Goncalves 25 years ago in Cannes when Young was showing Venus Peter. "I saw his film then and I talked to him about doing something, and there just came a moment a couple of years ago - thanks to the success of The Inbetweeners - where I was able to use the success of that film to get his film made. It's the first-ever co-production between Scotland and Portugal, in fact."

What do you do after you've made the most successful British comedy film ever? You go your own way. Christopher Young could say he always has.

Bannan screens at Filmhouse on Saturday, 8.40pm as part of the Edinburgh International Film Festival and is due for transmission on BBC Alba in September. The Invisible Life screens at Filmhouse on Wednesday at 8.20pm, www.edfilmfest.org.uk