British manufacturers are preparing for a re-run of the tense build-up to a Brexit deadline as the country awaits a new prime minister who threatens to leave the EU without a deal.

The UK is currently scheduled to leave on 31 October, forcing manufacturers to restart preparations for their worst-case scenario six months after the last scheduled exit date.

Carmakers in particular have run short of options, after previously rearranging their production schedules to try to avoid possible disruption in the aftermath of the initial 31 March deadline.

Jaguar Land Rover, the largest producer of cars in the UK, shut its main factories in April for a week to prepare for disruption to supplies. Germany’s BMW brought forward its annual maintenance period and Vauxhall planned upgrades to its plant for its new Vivaro van for the same time.

The production pauses dealt a temporary blow to the British economy, which shrank in the month of April, but a repeat in November would probably cause irrecoverable losses for carmakers, according to David Bailey, professor of business economics at the University of Birmingham.

Another round of production pauses “obviously would impact the bottom line” for carmakers, according to Bailey. “The [carmakers] can put workers on to flexible deals,” he said. “There’s an immediate impact on supply chains, who don’t necessarily have the flexibility.”

BMW, which produces engines and Mini cars in the UK, has confirmed that it will not close its factories again in November. The company has already diverted some engine production out of the UK to Germany to prepare for a possible no-deal Brexit. JLR declined to give details of its latest plans, although it is thought another shutdown is unlikely.

November shutdowns would be much more difficult, said sources at multiple major carmakers. “What was done in April was a bringing-forward of the summer [holiday], and you can only do that once,” said one.

There is also a mood of fatigue in some companies, with foreign executives unwilling to spend more on preparations that could be unnecessary for a second time.

Ian Henry, managing director at AutoAnalysis, said: “Several vehicle companies got their fingers burnt by investing so heavily for no deal at the end of March. Until they get a clearer picture, there’s no point spending more money.”

The six-month delay to the Brexit deadline has given some companies, particularly further down the supply chain, more time to make preparations

However, Tim Lawrence, head of manufacturing at PA Consulting, said carmakers had conversely been given some flexibility as they face a declining market across Europe, meaning they may be able to deal more easily with disruption to supplies because factories are not currently running at full capacity.

The six-month delay to the Brexit deadline has given some companies, particularly further down the supply chain, more time to make preparations that would not have been completed by 31 March, including stockpiling and making regulatory applications to EU agencies.

However, some firms have experienced steep warehouse rental increases since the first deadline, meaning that the price of stockpiling goods and materials has increased. Data from property services company Savills showed that top-grade rental prices for shed space in London and the south-east rose by 16% year-on-year in the first half of 2019.

The problem is compounded by the new exit date of October, in the run-up to the Christmas period when warehouse space is at a premium.

Ben Fletcher, policy head at Make UK, the manufacturers’ lobby group, said: “That presents both a cost challenge and an actual practical challenge of where you put the stuff.”

Make UK and almost every large manufacturer in the UK have warned repeatedly against a no-deal Brexit. With a new prime minister to be announced on Tuesday, executives are hoping that Boris Johnson, the clear favourite to win with bookmakers, will soften his position after a campaign in which he argued that the UK should leave the EU on 31 October, “do or die”.

“Is it bluster? Is it reality?” said one insider at a large manufacturer with knowledge of conversations with Johnson’s campaign team. “We’re hearing in the margins he’s far more pragmatic – there’s a lot of posturing.”

Multiple big foreign-owned manufacturers have warned that a no-deal Brexit could lead them to close British operations. Peugeot, the French owner of Vauxhall, has warned that it will only build its new Astra in Ellesmere Port if the UK avoids a no-deal Brexit, starkly underlining the importance of smooth-flowing trade for British workers at foreign-owned companies.

Airbus, the European planemaker, in January criticised “Brexiteers’ madness” and warned it would consider closing British plants in the event of a no-deal Brexit.