It could go for the so-called Norway option and become part of the European Economic Area. This would allow it most of the benefits of actual EU membership in return for having to still abide with most of its regulations and treaties, as well as controversially, for some, accepting free movement of labor from the EU. This status is also enjoyed by Iceland and Liechtenstein.

The main alternative to this is the Canadian model, which involves coming to an individual arrangement with the EU. It took Canada an arduous five years to complete its negotiations. The best deals under this arrangement would likely come with accepting much of the current EU rules, although opting out of free movement of labor would be possible. Switzerland and Turkey have also negotiated this arrangement.

The third alternative is for the UK to have no deal with the EU and operate under World Trade Organization rules, which could involve facing high tariffs when trading with EU countries.

Ambrose Evans-Pritchard, international business editor at the Daily Telegraph, believes the UK would seek the Norway-style arrangement.

"Britain would be free to negotiate free trade with anyone it wanted to. I would imagine the relationship between the UK and China would be better under such an arrangement. For the UK, it is a kind of soft exit also."

Ruth Lea, economic adviser to the Arbuthnot Banking Group and a leading Brexit campaigner, says the debate about the difficulties in agreeing new trade treaties is overblown.

"I actually went to the US government website after President Obama made his comments. I found the only trade treaty the US was negotiating was the TTIP (the Trans-Atlantic Trade and Investment Partnership between the US and the EU). You would think from what he said there would be 20 or so in the pipeline."

Lea, a former head of policy at the Institute of Directors, a leading UK business body, says it would be relatively straightforward for the UK to agree new trade arrangements with countries such as China.

"I took the trouble to speak to a trade lawyer so as to get the legal position clear. I found out that if we left the EU, we could go to China, South Korea or whoever and say to them whether they would like to continue with the existing trade agreement. If they said yes, we could just continue with the existing EU trade treaty."

However, Gideon Rachman, chief foreign affairs commentator for the Financial Times, believes a Brexit vote would conflict with how China views the UK as an important power broker within the EU.

"I would be slightly surprised if the Chinese were in favor of Brexit because I think they regard Britain both as a place for investment and diplomatic influence, particularly after the famous Xi visit," he says.

"The idea then was that Britain would serve as a key partner for them and be a relatively pro-China voice in Europe. If the UK voluntarily cuts itself off from the European Union, it tends to undermine that position."

Paul Cheng, a veteran Hong Kong businessman and politician with a keen interest in UK affairs, agrees that China sees Britain's role within the EU as useful to its overall relationship with Europe.

"They see Britain as a good influence on other countries in Europe in the way they look at China. China also puts a lot of weight and emphasis on economic issues, and they would prefer to have negotiations or agreements with the EU as a whole and not just to have to deal with countries separately."

Cheng, author of On Equal Terms: Redefining China's Relationship with America and the West, also thinks China sees the UK government as abrogating its responsibilities by holding such a referendum, a view shared by many in the UK.