They call it the Citadel of Hope because right now they haven't got a lot else to put in it. It is late January and the third national conference of the Occupy movement is being at a Salvation Army citadel in central Sheffield which has stood empty for 12 years. Before the Occupiers moved in, the floor was thick in pigeon droppings; now the bare brickwork is clean, and people from all over the world huddle in coats and blankets, crouched around a space heater under makeshift strip lights, sharing strategies for resisting police eviction and trying to work out what the hell to do next.

Four months after the start of the Occupy movement, which began in Manhattan's financial district and spread like a fever to hundreds of cities across the world, the press has begun to lose interest. There are no other journalists at the conference. No matter how many fluffy, media-friendly new actions the tireless Occupy organisers dream up, from melting Arctic ice on the steps of St Paul's Cathedral to staging mock-trials of former prime ministers at an occupied magistrate's court, they can no longer make editors hold the front page. The political establishment is making its message clear, in the manner of a hostess trying gently to expel the last unwelcome guests at the end of a party: stretching, ostentatiously tidying up and talking loudly about how cold it is outside.

On 18 January, the City of London Corporation won its high court action to evict the main London protest camp from the courtyard of St Paul's. The Occupiers have lodged an appeal, but believe that the tents, the kitchen, the large library and "Tent City University", which has run hundreds of free lectures and full-time courses in economics, could be cleared within days. The Bank of Ideas, the sister occupation near Liverpool Street housed in a building owned by the Swiss banking giant UBS, was evicted last week. As protest camps across the world, including the unaffiliated Democracy Village at Parliament Square in London, are turfed out by local police, even the BBC News website has published an article asking, "Protests: when's it time to go home?"

No going back

For many of the Occupiers, going home is not an option. After braving the past four months, during which the nature of this global resistance movement changed profoundly, many of those who have remained at the camps and squats over the winter cannot or will not return home. Some have been living on the streets for years; others have lost their jobs and homes only recently because of rent hikes and austerity measures. Many are among the million unemployed young adults in Britain, such as 19-year-old Tilly, who moved into the camps after finding she was unable to afford a place at university and who faces a court case for participating in a peaceful sit-in protest last year.

The idea that committed political operatives could be homeless is almost as disconcerting as the notion that homeless people could be committed political operatives. At the beginning of the actions, much of the press mocked the protesters for not being tough enough even to stay in their tents overnight, a slur later shown to be false. No one now could accuse these Occupiers of being faint-hearted: living in a protest camp is a short course in how to manage life outside mainstream society. It's a position that many more of us across Europe and America will find ourselves in as austerity programmes bite. It can feel like an adventure at first, but by the time you get to the hundredth day of sleeping on the ground or in an abandoned building, the process of taking and holding space has become plain old hard work.

At St Paul's, after tea and conversation in the canteen, I am invited into the art tent by Rob, who is 32. He has been living on the streets of London for 12 years. Being part of the occupations has given him back some confidence and a feeling of community. His drawings, complex abstract scratches in primary colours, are pinned to a paint board in a cosy sitting-room space inhabited by several smoking teenagers.

“It's the street people who are keeping the occupation going," he says. "They - I mean, the organisers - need to respect the street people more." When I tell Rob that I am here as a journalist, he asks if I was investigating anything. "I'd like to investigate you with my tongue," he says, putting an arm around me. "Let's make some occupation babies on the floor right here." I grip my cup of tea a little harder.

It would be unfair to note that sexual harassment has become a feature of life in the camps without mentioning that the Occupiers are taking the problem rather more seriously than most public institutions. One group session at the Occupy conference in Sheffield requires local occupations to report back on how they were maintaining "safer spaces" and protecting women and minorities while avoiding blanket exclusion of people whose social skills have atrophied from years of living on the edge of society. This "safer spaces" meeting descends into angry bellowing as young men shout over each other. Over lunch, a more enlightened male activist lamented that this often happens. "We had a simple solution to that at Greenham Common," says an older woman. "We just used to ban you all."

Lunch at the conference consists of tea, casserole and conversations about how the internet will alter the democratic process. You can tell a lot about any conference by the food. The last two Labour party conferences, for instance, offered bland, flabby quiche that managed to be both stomach-turning and insufficient. Occupy food is hot and plentiful even though it comes largely from skips at the back of local supermarkets. The groaning shelves in the kitchens at Sheffield and St Paul's give the lie to the myth of scarcity: at their peak, they were feeding thousands for free.

In Britain, the Occupy movements have become an economy of care, a network of mutual aid for those ground down by the job market, by the housing market, by the free market and all its intricate cruelties. During two weeks of hanging around occupied buildings in glossy, deserted business parks and at windswept tent cities in public squares; of sharing hot, sweet tea and vegetable soup cooked on gas heaters; of being shown around tenderly maintained propaganda installations, what almost nobody I spoke to talked about was the wider economy. Unlike three months ago, I heard few complaints about fractional reserve banking, wage repression or benefit cuts.

There are several possible reasons for this. The first is that the Occupiers may have assumed that, as a young person with straggly dyed hair and a selection of agitational badges on my backpack, I already knew the drill. That is a dangerous assumption. In the past three months, the Occupy movement has grown more insular, dealing with internal difficulties that divert energy from keeping the public message strong. The politics of this movement has also become more ingrained: its anti-capitalist discourse has not disappeared so much as soaked in, like a stain into a carpet.

When I visited St Paul's one recent morning, I found people making artwork and videos, or planning their latest fundraising project - a record label to promote political music and support the neediest Occupiers. For better or worse, Occupy is as much a cultural movement as it ever was a political campaign.

“This particular project was always going to be temporary," says James, 25, an anarchist organiser who was involved at the start of the occupations but who has now "critically disengaged". "To my mind, the eviction notice is an opportunity to consider who the people are who are left," he tells me. "On the one hand, it's the people who have nowhere else to go, and that's politically important. On the other, it's people who become zealots about this movement - those who've left their jobs, their flats, maybe even relationships . . . My fear is that, for those people, when the eviction happens there will be a profound level of trauma."

Designs for life

Traumatic as they will be, the evictions need not signal the end of Occupy. As the last few camps are forcibly broken up, Occupiers all over the world are moving into indoor spaces and squats, with a particular focus on "dead" real estate owned by big banking firms. In the US, the Occupy Our Homes project has been taking over foreclosed houses since early December; in the UK, it is larger spaces that can be converted into social centres.

A ragged-looking banner urging "Occupy Everywhere" hangs from the window of London's newest occupation in Frome Street, Islington, an enormous nine-storey corporate unspace recently abandoned by several City companies. Inside the building, shy, serious people in hoodies are clearing up mounds of rubbish, but outside not everyone is pleased. "They invited me in for a cup of tea but I won't be taking them up on it," says Amanda, who has lived in the area for over 14 years. "They've tried to make a point, which is a point that needs making, but it's been made."

Like most of the mainstream press, Amanda makes the mistake of thinking that Occupy was ever about concrete demands. Rather, it is about retaking psychic and physical space amid the self-satisfied centres of capital. It is about using that space to build tentative prototypes of a new social system, created by and for people failed by the present one. "Occupy was never going to be an agent of change," James says. "It is a portent of change."

The so-called 1 per cent can dismiss as many petitions as they like, but sweeping cultural transformation is the one thing that may yet have them running scared.