Executives from more than half a dozen automakers told Reuters at the Geneva motor show they hoped Britons would vote to remain in the EU in a referendum on June 23, concerned by the potential disruption to trade relations of a decision to leave.

"In terms of freedom of movement of goods, services and people .. our preferred option is that we stay within the EU," Rory Harvey, the chairman of General Motors-owned (>> General Motors Company) Vauxhall, said in an interview.

Executives from Toyota (>> Toyota Motor Corp) and Nissan (>> Nissan Motor Co Ltd), which runs Britain's biggest car plant, were also among those in favour of the country remaining in the EU.

Nonetheless, many said they were enjoying a drop in the value of sterling, which has seen it fall to a 30-year low against the U.S. dollar, caused in part by the uncertainty over the referendum outcome.

Britain's auto industry exports the bulk of the 1.6 million cars it produces a year, and a weaker sterling makes those vehicles cheaper for foreign buyers.

"It's good for Jaguar Land Rover (JLR)," its Chief Executive Ralf Speth said of the weaker currency. "Quite clearly this gives us a higher competitiveness all around the world so from an operational point of view, this is very good."

JLR was Britain's biggest automaker last year, making one in three of the vehicles produced in the country and exporting most of its high-end cars to markets such as North America and China.

However, Speth was still one of 200 business leaders to sign a public letter arguing Britain was better off in the EU.

Smaller manufacturers, such as sports car maker McLaren and luxury automaker Aston Martin, said they were also benefiting from the fall in sterling.

"I spoke to some of our U.S. dealers and it's a positive position right now," said Mike Flewitt, chief executive of McLaren, which sells about 50 percent of its top-end sports cars in North America and the Middle East.

Brands that do not build in Britain, or import more than their British plants manufacture, were concerned by the weaker pound, however, and that it might fall further in the event of Britain leaving the EU.

"Any strong exchange-rate effect will have an impact (on profit margins)," said Maxime Picat, head of brand at Peugeot (>> PEUGEOT), which imports all its cars into Britain.

McLaren and Aston Martin, which are less reliant on European markets than most other UK-based carmakers, said they would not take a stance on Britain's EU referendum, and Aston suggested nor should others.

"It's not a matter for a German, or a Japanese or an American to make an opinion on how a British guy or girl is going to vote," said boss Andy Palmer.

(Additional reporting by Gilles Guillaume, Andreas Cremer, Agnieszka Flak and Edward Taylor; Editing by Mark Potter)

By Costas Pitas