Theresa May asked the public to “come together”, after serving Brussels with the formal request to leave the European Union. But the Guardian’s three-month Brexit diaries project has revealed a nation deeply divided, between those texting their friends this week to say “happy Brexit day” – and others for whom the news brought only anxiety and fear.

Pollster Britain Thinks has been in contact with 100 diarists in 10 different locations – from Sunderland to St Austell – since January, asking them to report their hopes and fears about the dramatic political news.

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The responses, as well as a series of focus groups with voters from both sides of the Brexit divide, showed participants tended to fall into four groups, which Britain Thinks called Brexit diehards, cautious optimists, accepting pragmatists and devastated pessimists.

The diehards saw few risks or disadvantages from leaving the EU. As Ann from King’s Lynn put it this week: “I am writing this on Wednesday, listening to the news that the letter has been delivered as promised. I have texted people, ‘happy Brexit day!’” Another diarist described themselves as feeling “victorious”, while a third was “happy that the process is finally beginning and the UK can take the lead in its own future”. David, from Bradford, said the media were “just covering old news and arguments of ‘remoaners’”.

Cautious optimists thought the UK would probably benefit from leaving the EU. One described himself as “a bit happy and a bit nervous because I don’t know what is coming”.

Facebook Twitter Pinterest Pro-Brexit demonstrators wave union flags outside the Houses of Parliament in November 2016. Photograph: NurPhoto via Getty Images

Accepting pragmatists on the other hand perhaps voted remain, but have moved on, accepting that Brexit would happen. “I don’t really have any great emotion – possibly slightly nervous. However, I do also think as one door closes another opens, so not feeling depressed about it,” said Doreen, from Sunderland. Gabriella, from Bradford, said: “I try and keep an open mind and hope Britain will be ok. I am trying to be positive. We will have to see.”

For the devastated pessimists, however, this week’s headlines brought only, anxiety, sadness and fear.

“I feel sad and a sense of insecurity and uncertainty,” said Laura, from London. “Nervous, scared and worried,” said another diarist. “Sad and very nervous – I believe it will be a big mistake,” said Thomas, from King’s Lynn. “I blame Boris and his crew and I think they will go down in history as the men who sold the UK down the river.”

These divisions were also reflected in the diarists’ responses to the question of how the government should respond if, in the hard months of talks ahead, the EU appears to be offering Britain a raw deal.

“Keep calm and carry on,” said David, another King’s Lynn diarist, while several said “walk away”. However, even some of the leavers believed the best approach would be to “keep talking” and try to resolve everyone’s differences.

The Brexit diaries project found little evidence the public were ready to heed the prime minister’s advice and unite around her vision of a “global Britain”.

When Britain Thinks carried out a larger poll, of more than 2,000 people, more than two-thirds of respondents clustered at one end of the spectrum or the other – either seeing “no significant concerns” about Brexit, or “no significant positives”.

The Brexit diehards, who in general tended to be older, poorer, and live in rural areas, made up 37% of respondents. Devastated pessimists, who were younger, wealthier and more metropolitan, accounted for 30%. That left just 30% in the more moderate groups, with the rest not expressing a view.

This polarisation suggests the nine months since the referendum have done little to heal the divisions exposed by a hard-fought campaign. “The extent to which such a large proportion of the public cannot even countenance the views of the other side obviously poses major challenges for the key political parties, and appears likely to have significant repercussions for the way that politicians speak to voters in the future,” Britain Thinks’s Spencer Livermore and Tom Clarkson say.

Labour campaigned for remain, but is acutely conscious that its voters lie scattered across both sides of the Brexit divide, as evidenced by the large-scale rebellion when Jeremy Corbyn whippped his MPs to vote for the Brexit bill.

Tim Farron’s Liberal Democrats have modelled themselves as the champions of the devastated pessimists in the past nine months, pressing for a second referendum on the terms of the deal and protesting noisily about Labour’s quiescence.

May’s handling of Brexit so far is rated highly by our diarists, with three out of the four groups – everyone but those devastated pessimists – approving of her approach.

But when the respondents were asked who they would blame if the Brexit process didn’t go as smoothly as the government hoped, many gave the same answer – “Theresa May”. This underlines that the political stakes for the prime minister could barely be higher. And as she prepares to enter tough negotiations with her 27 EU counterparts, the hopes, expectations, and anxieties of Britain’s voters go with her.