Some people plan long layovers in large international airports so they can do holiday shopping in high-end, duty-free shops at a leisurely pace.

Others end up doing mad, last-minute gift-grabs at airport newsstands between flights.

London’s Heathrow Airport, with annual net sales of over $2.3 billion, believes both types of traveler can benefit from the services of a personal shopper. It offers such a service free, with no minimum spending requirement.

Travelers may request a personal shopper when they arrive at the airport, or book one in advance and send details about items of interest, preferences, the time they have on the ground, favorite brands and a shopping budget.

“By the time you arrive at Heathrow, your personal shopper will have pulled out suitable products and set them aside for you,” said the airport’s retail director, Muriel Zingraff-Shariff. “They’ll then escort you to each store and make new suggestions in line with your feedback.”

Since October, when the personal shopping program was expanded to everyone from a VIP-only service, hundreds have used it to buy everything from “a sandwich lunch to a gold and diamond watch” from the airport’s 300-plus retail outlets, Zingraff-Shariff said.

Arranging for items to be sent from a store in one terminal to a shopper in another is no problem, according to personal shopper Violetta Koltay. “But sometimes our biggest challenge is reminding passengers they have a plane to catch,” she said.

With more than 5.8 million passengers expected to pass through Heathrow this Christmas season, the services of the personal shoppers are even more in demand.

Koltay and other shoppers say passengers are seeking iconic U.K. products such as English tea, Scottish salmon and single malt whisky, as well as items made popular by the Royal Wedding, the Olympics and the birth of Prince George.

“The desirability of British brands has never been higher,” said Heathrow personal shopper Dana Jaber, “Visitors are keen to take home a little piece of the U.K. for their own Christmas celebrations.”

Heathrow’s personal shoppers have also noticed other trends among international travelers:

• English tea sold at the airport over Christmas is popular with Chinese passengers as a gift item.
• Turkish and Japanese passengers are key buyers of Scottish malt whisky “and are keen to understand the heritage of each bottle they purchase to take home.”
• Middle Eastern passengers are enlisting the assistance of personal shoppers to buy Scottish salmon, which is packaged and sealed for flight.

While a convenient amenity, personal shoppers no doubt contribute to an airport’s bottom line. According to a Heathrow spokesperson, while the average transaction value there is about $62 (£38), transactions rise to an average of about $1,625 (£1,000) when a personal shopper is used.

According to Airports Council International (ACI), revenue generated from retail rentals made up 27 percent of nonaeronautical income for airports worldwide in 2011—7.5 percent more than in 2010. (The ACI report tallying 2012 figures will be published in March 2014.)

“Retail has become a major source of revenue for airports,” said Raymond Kollau founder of Airlinetrends.com. “In fact, with the decline of sales via traditional retail stores at high streets and shopping malls, many consumer and luxury brands … are looking to open stores at airports, as this travel retail is still seeing a healthy increase each year.”

One problem is that many international passengers face a language barrier when shopping at an airport, Kallou said.

“Research found that having a knowledgeable personal shopping proactively approaching them to assist in a more educated and quicker purchase is very much appreciated.”

Kollau said that Frankfurt Airport was the first airport to introduce a personal shopper service for Chinese passengers at the end of 2012, followed by a similar service for Russian passengers this past October.

Heathrow’s personal shoppers speak a total of 11 languages, including Russian, Arabic, Spanish, French and Portuguese.

“I can imagine that Aéroports de Paris, operator of Charles de Gaulle Airport, which is the major gateway for Asian travelers to Europe, is keeping a close eye on how the service is being received at Frankfurt and London Heathrow airports, and will likely introduce a similar service soon,” said Kollau.

(My story about Personal Shoppers at Heathrow Airport first appeared on CNBC Road Warrior)