Britain votes on Thursday in a referendum to decide whether it should remain part of the European Union or leave.

Anyone from a Commonwealth country who lives in the UK and is registered can vote – estimated to be anywhere between 450,000 and 900,000 people.

And anyone with a British passport living in Australia – estimated to be about 1.2 million people, with 250,000 more in New Zealand – can also vote if they are registered.

Leaders of the remain and leave campaigns made their last-minute pitch to voters.

Global financial markets are preparing for a sharp bout of volatility if Britain does leave the EU, because London is one of the financial capitals of the world and the consequences of its splitting from Europe are impossible to predict.

Experts have said Australia would be unlikely to notice any immediate changes, because Britain would have to renegotiate trade and political links with the rest of the world. That would take at least two years and perhaps as long as 10.

But that didn’t stop Malcolm Turnbull warning it would be a “very big shock” if Britain left the EU.

“There will be obviously great efforts to ensure that the consequences of that shock are minimised,” the prime minister said on Thursday.

So what are the possible pros and cons for Australia if Britain does leave?

Migration

Leave supporters have said it could become easier for Australians to study or work in the UK if the country left.

At the moment, they say, Britain does not have the freedom to change a migration policy that favours the EU and discriminates against skilled workers from Australia.

The number of Australians migrating to and living in the UK has fallen dramatically over the past decade as Britain has restricted immigration with tough new visa rules, including a minimum income requirement.

The number of Australians obtaining work visas from the UK Home Office has halved since 2006 and is now fewer than 15,000.

If Brexit is successful, its leaders have promised an “Australian-style points-based immigration system” that would put an annual cap on visas, with about one-third going to skilled migrants.

That would let more Australian workers into the UK, because they would no longer be squeezed out by EU citizens with free movement within the union, they say.

Trade links

Australia and the EU have been preparing to hold preliminary talks about a free trade agreement.

If Britain left, those talks would likely be put on hold. Australia would have to negotiate a separate deal with the UK.

Britain would have to renegotiate its trade and political links with the 27 EU member states andthe US, as well as Australia, which would be a relatively low priority, the Australian British Chamber of Commerce chief executive, David McCredie, said. But if Britain remained in the EU, Australian businesses would continue to benefit from using the UK as a base from which to expand into Europe, he said.

Annmarie Elijah, the associate director of the ANU Centre for European Studies, said Brexit would be, “at best, a distraction and, at worst, a serious impediment”.

“In the event of a Brexit, an Australian government of either flavour will get on with the sound and close bilateral relationship with London and the improved broad-based relationship with Brussels,” she has written.

“The practical impact may be additional (complex) trade negotiations and major trade partners, which are more concerned with each other than third countries.”

The shadow assistant treasurer, Andrew Leigh, warned on Thursday that any renegotiation of trade agreements would have a disruptive effect on Australian businesses.

“For Australian companies that use Britain as an entry point to the EU, it would also generate disruption,” he said.

Economists say there would be consequences for specific markets and industries, such as Australia’s wine exporting industry, but the macro economy would not be seriously affected.

Britain is the top export destination, by volume, for Australian wines. At the moment they are subject to a tariff that is not imposed on wine exported from the EU.

Australian Wine’s regulatory services head, Steve Guy, said that tariff could be dropped if Britain quit the EU, making Australian wine cheaper.

Alternatively, a tariff could be introduced for all imported wine, creating a more level playing field for Australian exporters.

Or Britain could choose to impose new technical rules, such as those covering labelling, for imported wine, he said. That might involve extra costs and be a “nuisance” for Australian wine exporters who are already covered by an EU treaty.

Currency

The Reserve Bank governor, Glenn Stevens, noted in the RBA’s most recent interest rate meeting that uncertainty about the outcome of the referendum had increased expectations of volatility in the pound’s exchange rate against the US dollar.

Currency strategists say if Britain leaves the EU, the Australian dollar could fall by about 2c on Friday compared with the US dollar, from 75c to 73c.

But that would only be a short-term hit. The value of the dollar won’t be affected in the long term, they say, unless people believe the global economy will be hit significantly by the change.

“And the chances of that are very small,” Joe Capurso, a Commonwealth Bank currency strategist, told Guardian Australia.

They also say the reverse will happen to the dollar if Britain remains in the EU. If that happens, the dollar could rise by about 1-2c on Friday.

“By 1pm tomorrow [Friday] we expect to have three-quarters of the regions counted, so we should know the result by then,” Capurso said.

“If you’ve got three-quarters of the vote, you should know what the answer’s going to be, unless it’s neck and neck.”

What if the vote is in favour of staying in the EU?

The desire of many Britons to leave the EU will not dissipate if Brexit fails.

Experts say there could well be another similar campaign in the future. When Britain joined the EU in 1973, a referendum was held just two years later, in 1975, on whether to stay. The result was two to one in favour but the “British question” was not resolved.

“The possibility of a Brexit has been close to the surface of British domestic politics ever since,” Elijah said.

“It fuels the imagination of Eurosceptics across Europe and invites speculation from those who would reconfigure the UK’s place international politics.