LONDON — Some car manufacturers will idle their factories. The police are advising store owners to hire more security guards. Trucks have been sent to the coast to practice with artificial traffic jams. And exasperated business lobbyists are warning of supply-chain calamities.

Britain remains politically paralyzed ahead of a contentious vote in Parliament next week on a plan to withdraw from the European Union, or Brexit. But businesses are plowing ahead and preparing for the possibility that the country crashes out of the bloc without an agreement at the end of March — a no-deal Brexit.

Honda, the Japanese auto company, which produces about 150,000 cars a year in its factory in Swindon, in southwest England, said on Friday that it would stop production for six days in April to assess its supply chain and possible disruptions from border delays after Brexit. The company said its 4,000 employees would go to work but would be training or handling maintenance.

BMW has already said it will shut its Mini factory in Oxford for maintenance for a month beginning April 1, in case a no-deal outcome disrupts its production.