About 250 alumni of British scholarship schemes have pressed No 10 to speed up its evacuation of Afghan Chevening scheme students, who had still not been contacted with a plan for their escape from Kabul by Wednesday morning.

Three days after Boris Johnson promised to help them, several of the 35 students with UK government-funded scholarships said they were extremely anxious, suffering panic attacks and fearful of their futures as they had still received no concrete advice from Britain.

With the delay in contact from the UK and the window for rescue flights closing, it is understood some of the students have got on to Italian and US evacuation lists instead.

In a letter to the foreign secretary, Dominic Raab, the alumni of Rhodes, Gates, Marshall, Clarendon, Commonwealth, Chevening and other scholarship programmes called on the government to ensure the safe passage of the 35 Afghan students in time for their courses at British universities, saying the scholarship “could be lifesaving” in light of the Taliban’s position on education.

A Home Office source said Priti Patel, the home secretary, had stepped in to expedite the students’ visas, after the prime minister said they would be helped. Johnson’s intervention on Sunday reversed a Foreign Office decision to withdraw support for them coming to the UK this year, which said they could defer their scholarships for a year.

“It should never have happened and Priti has had to fix it,” the source said, adding that arrangements would be made for the students in the coming days.

A Foreign Office spokesperson said it was “contacting them today to arrange their travel to the UK as soon as possible” and the ambassador had written to them to update them on this development.

However, on Wednesday morning the students said they were still in limbo, with one telling the Guardian they had only received a single email from the embassy “confirming that they are in discussion with higher authorities and will update us on progress”.

Their biggest worry is about the difficulty of reaching Kabul airport, with a UK government source acknowledging the students would have to make their own way there to try to get an evacuation flight once the visas are processed.

A No 10 spokesperson said: “I certainly believe we’ve been in contact with all of them now to honour the visas that they applied for. In terms of wider support to get them there, that would fall into the similar challenges that we have more broadly with those who may be eligible for resettlement. We will do what we can and advice is available through the [Foreign Office].”

Dr Nishank Motwani, the director of research and policy at ATR Consulting in Kabul, and who is in contact with a number of students, said the scholars had received no contact since the initial email and were growing increasingly anxious as the Taliban consolidate their control of Kabul.

“Everyone knows that the window for evacuation flights is shrinking every day. And with every flight that these students see or hear take off, they are thinking ‘how many more planes will get out?’. They are becoming increasingly anxious.”

While Kabul airport has been secured by the US military, the Taliban control the checkpoints leading to the airport, and the road leading to the terminal is chaotic and potentially dangerous.

“It’s like a funnel, that road leading to that entrance to the airport, it is extremely crowded, a riot-like situation. Nobody wants to subject themselves to that mayhem, where they could potentially lose their lives.”

Motwani said the already anxious students faced an “information vacuum” from their universities and the British government. Electricity is unreliable in Kabul, meaning phones and computers run flat, and there are fears mobile and internet networks may be cut, or stop working, so messages will not get through.

“The combination of these, and the fact the Taliban are everywhere on the roads is making it very difficult for these students to keep up hope,” Motwani said. “They are still hopeful, don’t get me wrong, but when there’s no information, it’s hard to keep that up.”

Caoilfhionn Gallagher QC, a former Chevening scholar who is trying to help the students, said: “The last minute U-turn by the prime minister on Sunday night, agreeing to reverse the unconscionable decision to halt the Chevening scholars’ awards for this academic year, may have lowered the political heat on the UK government over this issue.

“However, this is an empty promise without an accompanying evacuation plan from the UK government for the 35 Chevening scholars and speedy, practical action. They were selected by the UK for this prestigious scholarship; they made life-changing decisions on foot of this and placed their trust in the UK. They are now at grave risk in Afghanistan, and remain without practical, concrete plans for their travel. They have been badly let down, and there is a moral obligation on the UK to put this right.”

Prof Ronan McCrea, who jointly organised the letter to the government with Gallagher, said: “It’s wonderful that this policy has been changed, but to be of practical benefit it is essential that both the UK government and the hosting universities take the steps necessary to ensure that the students can actually take up this opportunity.”