Most MPs may now be on the beach, but for those worried about the chances of Britain crashing out of the EU with no deal it has not been the normal break in the sun.

For a start, the holiday reading list has been less entertaining than normal. Standing order 24, paragraph 2.7 of the cabinet manual and section 2(3) of the Fixed-Term Parliaments Act have become the must-reads of the summer. Family outings have been interrupted by battles to find phone reception at various beauty spots to talk to opposition MPs.

After a week that saw Boris Johnson and his key adviser Dominic Cummings make clear threats about leaving the EU whatever the cost at the end of October, concerned MPs have already begun to plan. New governments, emergency legislation, breaches of convention and court cases are already being proposed by what several described as the “rebel alliance”. Many anti-no deal MPs are also concerned about the lack of coherence so far. All those who spoke to the Observer had doubts that no-deal Brexit could be avoided.

“Everyone has to pull together, and that is never a guarantee,” said one former Tory minister trying to coordinate efforts. “We are trying to hold together an unholy coalition of moderate Labour, Labour frontbench, Lib Dems, Scottish Nationalists, minor parties, independents and moderate Tories. It’s difficult.” However, details of some of the plans are already emerging.

Anti-no deal laws

Senior figures within both the Labour and Conservative parties believe that the simplest way to stop no deal is through a new law, forcing the prime minister to ask for an extension to Britain’s EU membership. This is the focus of early efforts.

The rebels see two possible routes. The easiest move is to hijack any legislation that the government proposes in the autumn. Yet the plotters know that the government may simply refuse to propose any new laws to avoid such an ambush. “The moment there is legislation, we can amend away,” said one plotter. “But their strategy is clearly not to legislate about anything and have endless debates in parliament about the colour green instead.” A senior Labour figure added: “There is legislation needed to do a no-deal Brexit in a responsible way, but we can’t assume that Johnson and Cummings will do it.”

There is a second route that most believe will have to be tried – the unusual move of backbenchers seizing the parliamentary timetable from the government in order to pass their own laws. It will not be easy and will probably require breaches in convention by the Commons Speaker, John Bercow. There is talk of MPs calling an emergency debate and amending it for their purposes – something that is not normally allowed. Precedents are set to be parked.

Toppling the government

While some in Labour are pushing for an immediate vote of no confidence in Johnson when MPs return in September, it is already becoming clear that this would have a better chance of succeeding closer to the Brexit cliff edge. One anti-no deal Tory explained: “I would find it hard to no-confidence the prime minister before he had really done anything.” Others, like the former Tory attorney general and rebel figurehead Dominic Grieve, have said they will do it if necessary. Voting to remove Johnson, however, is the easy bit. A no-confidence vote starts the clock on a two-week period to find a new government – and an election is called if a replacement cannot be found. Proposing the date of that election technically falls to Johnson – with suggestions that he could set it for immediately after Brexit day.

An obvious problem with the alternative government plan has already emerged. As leader of the opposition, Jeremy Corbyn states that it should be led by him. Yet the Lib Dems and moderate Tories will support only a temporary administration headed by a neutral figure. The stand-off has led to an outbreak of what has been dubbed “Meatloaf Remainerism” (I would do anything to stop no deal, but I won’t do that).

The latest iteration of the “alternative government” plan assumes that Corbyn has the right to try and fail to form a government. Then, a third option – a government probably headed by a moderate Conservative such as David Lidington – is being considered.

It would request a Brexit extension and call an election. “It is not a government of national unity – it is an emergency government,” said one supporter of the idea. Without the Labour leadership’s support, it is hard to build a majority for such an idea, but a surprising number of MPs are at least entertaining it. “I think it would be very challenging to get a parliamentary majority behind one name, but anything might be possible in the autumn,” said a senior Tory rebel.

The courts

Could Johnson prorogue parliament? Could he refuse to resign after a no-confidence vote? Could he name an election date that falls after Britain has left the EU? Should the Queen simply dismiss him? These are all threats that have been raised by Johnson allies – and steps are already being taken to test them in the courts.

The Observer understands that a legal action aimed at preventing Johnson from shutting down parliament to force through a no-deal Brexit, lodged last week, has been given permission to proceed. A timetable for the case is expected to be agreed this week. The case has been lodged in Scotland by Jo Maugham QC’s Good Law Project.

Other legal teams are drawing up a case designed to prevent Johnson from refusing to resign should he face a no-confidence vote – and also limit his powers to circumvent parliament more generally. They believe that the sabre-rattling from No 10 could help them, as it may help prove a willingness by the executive to exclude parliament.

Hold fire...

There is already frustration that all the talk of constitutional tweaks and breaches of convention is exactly what Johnson and Cummings want – the spectacle of Remain MPs using obscure devices to prevent Britain leaving the EU. They argue that it is the perfect context for Downing St to wage a “people vs parliament” election campaign that unites Leave voters under the Conservative banner, giving a majority to Johnson. They are proposing an alternative approach: allow some of the real effects of a no-deal Brexit to become clearer, and concentrate on the fact that such an outcome is profoundly undemocratic.

As one recently departed cabinet minister puts it: “The focus on process helps Cummings, frames the debate as people vs parliament and crowds out the focus on the big questions about the substance of no deal. My side of the argument needs to get away from process on to substance.”

The People’s Vote campaign for a second referendum has similar concerns. “Cummings wants to pretend anyone against the imposition of no-deal is somehow undemocratic by focusing on arcane procedures and parliamentary instruments,” said a senior campaign source. “We will be using the next few days to reassert fundamental democratic principles about why Johnson cannot force no-deal on the British people when he himself ruled it out in 2016.”