In the third part of his trilogy on the life of Jesus Christ, published this week in time for the Christmas rush, Joseph Ratzinger, Pope Benedict XVI, seemed curiously at pains to prove that the traditional nativity wasn't quite gospel. Most headlines were made by his insistence that no ox and ass had been present in the stable at Bethlehem – as if that were the most outlandish aspect of the greatest story ever told – but along the way he also took a swipe at the idea that a heavenly host of angels appeared to shepherds and sang of the virgin birth. The pope had no problem with the general thrust of that particular scene – cherubim, seraphim, the angel Gabriel himself, glory shining around, all of that – but what the pontiff did have a serious difficulty with was the idea that the angels sang their good news. Far more likely, he suggested, was that they spoke it. Which goes to prove the point that there is no fun in being infallible if you can't also be pedantic.

For most of us, I guess, such papal revisionism won't result in too much seasonal anxiety beyond perhaps a momentary pause should we come to belt out "hark the herald angels sing!" at a carol service. If they can't even agree on that bit, you might wonder, where does it leave all the rest? My own faith in angelic intervention in worldly affairs has never extended beyond an annual, and generally tearful, family homage to the bumbling Clarence who saves Jimmy Stewart from despair and suicide and wins his wings in It's a Wonderful Life; which is to say I don't believe in God, but I do believe in Frank Capra.

It comes as something of a surprise, in this sense, then, to discover that for a large proportion of British people, angels – whether singing or speaking – are something slightly more real than that. In the most recent survey of opinion on such matters conducted by ICM for the Bible Society in 2010, 31% of the population professed a clear belief in angels, only 51% said they did not believe, and 17% were unsure. This concurred with a YouGov inquiry asking the same questions in 2004, suggesting that heavenly minions were essentially recession-proof. The ICM survey found that belief was higher among British women (41%) than men (23%), slightly more common among over-45s than those aged 18 to 44, and more prevalent in London, where 40% of people of all creeds professed a faith in angels, than elsewhere.

I imagine that a good few of the positive respondents in those surveys believed in angels in the way that Abba believed in them, or Robbie Williams did. However, even when the questions got more pointed there was still a degree of certainty. Slightly fewer than 29% of adults believed they had a guardian angel watching over them personally; 5% claimed they had actually seen or spoken with an angel (though in Nottingham for some reason, this figure rose to 17%).

Such statistics, I suppose, go some way to explaining the recent success of a host of books based on personal experience of angelic encounters. These books include Peter Williams's The Case for Angels, Emma Heathcote-James's Seeing Angels and the work of M Scott Peck, author of The Road Less Traveled, but leading the phenomenon – the Fifty Shades of Grey of angel literature – are the books of a 58-year-old Irish widow and mother of four named Lorna Byrne, the latest of which, A Message of Hope from the Angels, has just been published.

Since she brought out her first memoir, Angels in My Hair, four years ago Byrne has sold well over half a million books in 50 countries with books translated into 27 languages, including Mandarin, Japanese and Korean. Websites and chatrooms abound, creating a burgeoning industry for other angel watchers. Byrne's publicist at Hodder & Stoughton suggests to me that the trend for this kind of spiritual conversation has replaced the previous growth market for "misery memoirs"; possibly the shift is something to do with economic doom and gloom – in recession people would rather hear about other people's miracles than their despair.

In any case, the other week I found myself alone in the publisher's office to talk with Lorna Byrne about her experiences. I say alone, although to Byrne, a soft-spoken and convincingly sincere woman with a habit of looking past you and smiling every so often, we are anything but. The room also contains, to her eye, a dozen or so heavenly bodies crowding around the meeting table.

Byrne's account of the miracles of her own books rests quite heavily on the fact that she is distinctly dyslexic and still can't really read or write. "When I was a child the angels used to tell me I would write about God and them," she says, "but I didn't used to take any notice of them… but even when Angel Michael said to me that it is getting near your time I was telling him, 'Stop pestering me. How does God expect me to write a book when I can't read or write at all?' He said help would be sent to me. And it was."

Help arrived in the form of a smart agent, a Dell laptop, and a "magic box", a voice-recognition tool that allowed Byrne to get the story of her visions down on paper. "It filled me with fear of being laughed at and ridiculed," she says. "But right from when I was a child the angels told me that my story would go all around the world, that it would be a bestseller, though they did not use those words." And so it has come to pass.

In a way, Byrne, of County Kildare, believes she had to wait for her moment. "With the Celtic Tiger disappearing and the financial crash I would say that is a wake-up call to tell us we are following the wrong path…"

She must have been impatient though, I say, to tell people what she could see. "My parents never let me talk about any of it," she says, "which goes back to when I was two and a half. I was always distracted seeing my little brother [who died as a baby] and I thought he was flesh and blood and I would play with him by the fire. He would always sit nearest the fire because the fire would not burn him and then one day his hand went into mine and there were just these amazing sparks. I knew then that he was a soul, but I was told to tell no one at that time but the angels…"

Was she aware of anyone else seeing such visions as a child?

"Well I know some little children see angels," she says. "If they say something they are told it is their imagination or an imaginary friend or something. But it isn't always."

You must have felt different?

"I did. It made me lonely. Because I couldn't share what I knew."

She told her late husband, Joe, who died of cancer not long before she started writing. "He turned to me and said, 'Lorna, only priests and nuns see angels', and we hardly spoke about it again." Over the years, she says, she has met other people who say they see angels but they do so in meditation, or prayer, not in everyday life.

Doesn't it get claustrophobic, always in a crowd? I wonder.

"Sometimes I will say, 'Leave me alone', but it doesn't work." She shakes her head, ruefully. "I can't hide from them."

Each culture has explained people who claim such visions in terms of its prevailing wisdom. For a large part of human history – right up until Joan of Arc in the west – and even into the present in certain societies angel-seers were credible enough to go to war over, and to give your life for. In the past century they were given psychological explanations by Freud and others. These days neurobiology seems to provide answers.

In his latest book, Hallucinations, the celebrated neurologist Oliver Sacks examines a history of "seeing things" and "hearing voices" that takes in the mysteries of angelic visitation among many other things. He tells the tale, for example, of the bus conductor who suddenly, as a result of some kind of epileptic-style brain seizure, is convinced of heavenly revelation, and exists as he checks his tickets in the kind of euphoria that seems to have fuelled the poetry of William Blake. When I spoke to Sacks recently he talked of "people these days seeing UFOs in the way that in the past they used to see angels". His book comes up with all sorts of physiological reasons for the unexplained, but it also leaves a tiny space for mystery.

In recent years there has been much clinical work to try to fill that mysterious angel-shaped gap. One landmark 2010 study of neurosurgical patients found that the removal of certain parts of the brain could increase the predisposition to a belief in supernatural power. Having mapped the presence of tumours in the brains of a significant sample of patients and interviewed them about their religious beliefs before and after surgery researchers at Udine in Italy discovered that those with particular types of tumour in the posterior of the brain were far more likely to talk of the presence of God and the experience of visions.

Other work using brain scans has shown the mystical experiences of Tibetan Buddhist monks and Carmelite nuns to be associated with unusual or altered activity in this region of the brain, though of course this can be interpreted in a number of ways. In America, where 80% of people profess a faith in angels, and more than half say they believe that such supernatural agents shape the detail of our lives, some scientists have taken this particular brain function as evidence of the power of prayer and our inbuilt ability to understand the divine. Others are not so sure.

Michael Alper the author of The God Part of the Brain, favours materialist explanations. When Lorna Byrne brought her books to the States, where they have found six-figure advances and ready audiences, he suggested there were only two ways of explaining Byrne's visions: "Either a) she actually believes it, or b) she is a complete charlatan," he observed. "There is no option c) – that she would be talking to angels. Human beings are simply genetically predisposed to believe in some kind of spiritual reality," he argued, suggesting the idea of someone to watch over us is an evolutionary coping mechanism to help deal with death.

Byrne herself has heard all of these arguments before of course but she holds on to the irrefutable get-out clause of the visionary or the priest: she sees what she sees. After a while, talking to her, I feel I might just as well rattle through a few traditional orthodoxies. If we all have a guardian angel, why don't they step in, Clarence-like to keep us from harm, I wonder at one point.

Byrne smiles over my shoulder, as if sharing a private joke about the old ones being the best. "People contact me from all over the world who have known people who have committed suicide asking how could they do that if they had a guardian angel, and I say, well, they didn't realise it. That's the terribly sad thing. We all have free will…"

Does she see herself in a line of prophets seeing visions?

She does, though she has no idea why she has been chosen.

In her latest book she makes the point that Christmas is a particularly busy time for angel watchers. Has it started yet?

"It has," she says. "In November they all arrive with their little balls of light. I see then coming down as if down a hillside or a mountain."

Has she seen the Angel Gabriel?

"He is an odd angel. Very beautiful. I never knew it was him, because he would often be there dressed as a biker…"

As a biker?

"Yes, something like that. I always wanted to reach up and touch his face. Would I say he is more incredible-looking than Michael the Archangel? I would have to say yes."

And what about the angels in the room with us now? I say. What are they up to?

She has a quick look round at the stacked bookshelves and desks, checking them out. "Let's say some of them are unemployed at the moment."

Are they just loafing about, I wonder, or eager like interns?

"Well," she says gently, "they are waiting to give you a helping hand." She listens for a moment. "I am told by them that you are always looking for a helping hand," she says, "when you want to know what to write. One of them even has a pen and paper in hand." She looks again and chuckles.

"Your guardian angel is giving a male appearance, really strong," she says. "He is standing about three feet behind you but enfolding you. And the cloak is this beautiful green and I smiled at him because he is showing me the emeralds all embedded in it. He just showed partially his wings, a fleeting appearance, but very wonderful, not feathers or silk, more like the air, and alive. Very alive. He won't let you down…"

That is good to know, I say. But can she tell me more about the ones with the pen and paper, how exactly does that bit work? You see I've got this tricky story about angels to write…

She smiles. "Just wait and it will happen," she says.

Well, I say, I'll believe that when I see it.

A Message of Hope from the Angels by Lorna Byrne is published by Hodder & Stoughton, £9.99.