China spent $129 billion on international travel in 2014, says the United Nations World Tourism Organization. A happy coincidence of rising disposable incomes, fewer restrictions on foreign tourism and a currency that has appreciated mean Chinese are traveling more and, consequently, spending more than they did 10 years ago.

In the West End of London, Chinese visitors account for more than 20 percent of all tourist spending.

"There has been a phenomenal uplift," said Jace Tyrrell, deputy chief executive of New West End Company, which represents 600 businesses in the area. "In 2014, Chinese shoppers accounted for over a quarter of tax-free sales on Bond Street, with visitor numbers from China increasing by 79 percent over the last four years and expenditure rising from 184 million pounds ($284 million) to 492 million pounds."

It is not just overseas retailers that are snapping at the heels of China's high-end boutiques, it is overseas e-tailers too. New York-based Gilt sells heavily discounted designer items over a restricted period.

Marshall Porter, senior vice-president and general manager of international at the US firm, said: "We've had the Chinese language site for almost six months. The navigation is in Chinese and so is the checkout. We're trying to create a site that is seamless for the cross-border Chinese shoppers."

Shi Jing contributed to this story.