At a Best Buy store in downtown Chicago, Charles Dunstone, chief executive of Carphone Warehouse, is being given a tour by shop manager Pablo.

"This is an urban trendsetter store," says the affable manager as he walks through the 45,000sq ft retailing warehouse.

That makes his typical customers 19-32 years old, with incomes of anything from $20,000-$100,000 (£11,520-£57,600) a year and, for the purposes of the Best Buy team, their names are "Carrie and Buzz".

They are quite a different crowd to the mid-American market which Best Buy mainly serves through the vast interior of the US.

Those customers - "Maria and Ray" - like to shop with their families, have blue-collar jobs and earn anything from $40,000-$80,000 a year.

Down by the gaming section of the store, Roger Taylor, Carphone Warehouse's finance director, is pondering what Carrie and Buzz's UK counterparts might be called.

His thoughts matter because Mr Taylor is also chief executive of the European joint venture between Best Buy, the leading US consumer electronics retailer, and Carphone Warehouse, the UK's largest mobile phone seller, which is due to start rolling out up to 200 European outlets under the Best Buy format in the middle of next year.

Sophie and Charlie is "too West End", according to Mr Taylor. "It has to be snappy," he says.

He rattles through some names - Simon, Tom, Susan - and stops on Anna and Andrew. "Now those names apply to the urban trendsetter across the UK," he jokes.

Making up customer names may seem a little silly, but it is exactly this "know-your-customer" approach that Best Buy and Carphone Warehouse hope will help them hit ambitious targets and distinguish them from some rivals' more laissez-faire approach as the economic downturn intensifies and looks set to last for some time.

It is a brave venture in difficult times.

By 2013, 100 stores are due in the UK, with capital expenditure running to £350m. Best Buy and Carphone Warehouse will contribute £175m each.

Mr Dunstone has promised Best Buy Europe will generate sales of £6.2bn and operating profit of £348m by 2013, which implies a 5.6 per cent margin.

He is also targeting a return on invested capital running to a mid-teen percentage.

To put that in perspective, competitors Kesa - owner of Comet - and DSG International --which runs PC World and Currys - have operating margins of just 1 per cent.

Faced with such a challenging market, Mr Dunstone is typically optimistic. No matter that purchases of flat screen televisions, laptops and home cinemas fall off the shopping list when consumers are fretting about paying their mortgages during an economic downturn. He believes that Best Buy Europe has something new to offer, not least the promised superior service. "If you go to a lot of electrical stores now, they just keep the rain of the stock, no one there does anything, they don't display it nicely, if you ask a question they just read the label back to you," he says.

Some analysts argue Mr Dunstone's margin target is attainable.

Assad Malic of Credit Suisse says: "The strategy, if executed as presented, should offer a meaningful opportunity for creating shareholder value as well as exert further pressure on Kesa and DSGI." Mr Dunstone knows he has to change his business model radically if his UK company is to survive.

He founded Carphone Warehouse in 1989 and it enjoyed rapid growth by putting mobiles into the hands of consumers across Europe.

But Europeans now all own mobiles and they are buying fewer replacement handsets because of the downturn.

Best Buy Europe will therefore sell a gamut of wireless devices that go well beyond mobiles.

Best Buy is the senior partner in Best Buy Europe and some analysts say Carphone Warehouse's decision to form a joint venture with Best Buy could ultimately lead to the UK company's disappearance. Mark James of Collins Stewart predicts a demerger of Carphone Warehouse's retail and telecommunications businesses that could enable Best Buy to buy the UK company out of Best Buy Europe. A demerger could also enable another telecoms company to buy the other half of Carphone Warehouse, its fixed-line broadband business.

Mr Dunstone, asked whether he still sees himself at Carphone Warehouse in a decade, is enigmatic. "I don't know if it will be called Carphone Warehouse," he says, "but I still see myself being involved."