“WHAT I like doing,” says Sue Bourne, “is finding the extraordinary in the apparently ordinary. That’s what I’ve gone looking for.”

Bourne is often cited as one of the top documentary directors in the UK – a status she has gained not through making grand investigative works, but seemingly small, personal films. She makes documentaries that change the way we feel and talk about ourselves. Films like The Age of Loneliness, which helped trigger a nationwide debate on the epidemic of loneliness. Or Fabulous Fashionistas, which delved into the lives and wardrobes of six elderly women who were defying the expectations of old age and dressing outrageously.

Her most recent film, A Time To Live, gives us a window on the lives and thoughts of twelve people who have terminal cancer.

“For me,” she says, “the film’s about life, not just facing death. I thought these people will know how to live. They’ll have found the trick to what really matters. That’s what I was looking for. What does matter?”

The result is a tearjerker, but one that is joyful and challenging. Here, for instance, we find Fiona, who says cancer has given her such insight that now, if she had a chance “to live longer and not have cancer and not have the insight I’ve got I would not take it”. Or Annabel, a former housewife whose first act on her bucket list was to leave her husband. And Kevin, who declares, “Being told you have terminal cancer doesn’t have to be a death sentence – it can be a live sentence.”

There is a Sue Bourne brand. Often she tackles subjects that are, on the face of it, in comfortable British society, our most gloomy and challenging issues, yet somehow manages to make from them something uplifting. They’re the universal struggles – growing old, being lonely, coping with the gradual loss of a loved one to dementia, knowing that you will soon die.

When we first talk she is at her cottage in Dumfries and Galloway, a second home, away from her main base in London, and she is just about to go horseback riding on the beach. That alone makes her sound like a woman who knows how to grasp life.

She hasn’t, she says, always been like this. “Before I did grasp life, but in a highly-stressful, highly-Scottish way – drinking, smoking, working too hard, totally stressed out of my box. I’ve changed a bit. I do love my work but I’m not going to kill myself doing it.”

The subject of her film has a personal resonance. In her early fifties, while filming her documentary about her mother’s Alzheimer’s, Mum and Me, she was diagnosed with breast cancer and had a mastectomy. While for her it wasn’t a death sentence, it was a blow.

“Once you’ve had cancer, you are in a club,” she says. “And that club is that you’ve had your nose squashed up against your own mortality. I kind of skidded to a halt and looked at my life quite closely and I thought okay, okay, that was a warning shot over my bows, and I can either ignore it and go back to all my old habits, or change.”

She has already formulated, she thinks, her own answer to what she would do if given months to live. “You spend time with the people that you love. And you really do make the most of every day.”

Bourne’s most successful films have been prompted by events and issues in her own life. My Street, her award-winning exploration of the people who lived on the street she had lived on for 14 years, was triggered by a nosiness about the neighbours.

“Fabulous Fashionistas,” she says, “was about, okay, I’m going to get old, how do I live a marvellous, exciting, interesting old age that defies expectation?”

She grew up in Ayrshire, and, though she spent most of her working life in London, she describes herself as "so Scottish”.

As she puts it, “I'm Scottish in terms of my nature, how I think about things, my morality, what I think is important. I’m a right difficult, tenacious sort. I know I am. I fight for my films.”

And she fights and works frequently on her own – her company, she says is “only me”.

Bourne’s life and career, which originally began at STV, didn’t always run smoothly. “I had a really marvellous first few decades,” she says, “and then I hit my fifties and everything got really tough. My mum had Alzheimer’s. I’d split up from [her daughter] Holly’s dad so I was a single parent getting her through school, working flat out, coming up and down to Scotland to see my mum when her Alzheimer’s got worse. And then I got cancer.” She pauses and sighs. “No surprises.”

She adds, “Then, the same time, I got cancer, Holly’s told me that he [Holly's dad] had terminal cancer. He subsequently died. And then my mum died. So they all died round about the same time. And I think that’s when I did slightly hit the wall.”

In A Time To Live, Bourne refrains from telling us who has since died. She took a similar approach in her film about her mother’s Alzheimer’s, Mum And Me. “I didn’t want to keep filming Mum till she got really poorly or have to say, on the film, my mum died. So I left it with her just running around having hysterics, laughing. I left it saying, ‘I don’t know how long my mum’s got, but Holly and I and Mum intend to laugh as much as we can for as long as we can.’”

She felt the same desire with A Time To Live. “If I say who’s dead,” she says, “that’s all you remember. I don’t want that. I want you to listen to what they’re saying and remember their beautiful, smiling positive faces.”

A Time To Live is on BBC2 on Wednesday, May 17 at 9pm.