The jumble sale image of charity shops has long disappeared, but many people would be surprised at the hard work that has gone into their recent transformation.

As well as design makeovers to update them for modern shoppers who no longer like picking over old shoes, bric-a-brac and incomplete jigsaws in fusty surroundings, they have also come under the harsh light of commercially-driven competition.

Recently, television viewers saw Save the Children's experiment, overseen by the retail expert Mary Portas, who cleared out the clutter — and octogenarian staff, replacing them with clothes made by local fashion students and a professional manager.

The Oxford-based charity Helen and Douglas House has had no problems adapting to the new era, because it had no charity shops at all until 2003, when it inherited the lease from a former florist in the Covered Market.

The charity's head of retail, David Cryer, said: "It's very small — not much more than a kiosk — so it concentrates on gift items and bric-a-brac. Quirky is the word we use to describe it. It was a one-off and not a sustainable model. The trustees were not sure what to do next, and that's when I came in."

Mr Cryer, 52, was brought in five years ago from Marks & Spencer, where he had helped to expand the Simply Food shops. As the first children's hospice in England, Helen House was used to breaking new ground, but the trustees were cautious about committing to invest £40,000 per shop to generate a fundraising stream that was far from guaranteed.

Their decision has more than paid off, and the chain of shops has now reached critical mass, set to generate £500,000 a year profit — a welcome boost at a time when the charity is facing a fall in donations because of the recession, and is expecting more demand for its services and less local authority funding as public-spending is cut.

The Helen and Douglas House post came up at just the right time for Mr Cryer, who says he always intended to leave his corporate career for the voluntary sector, and was keen to move out of London with his young children.

Was it a shock to move from such a hard-nosed competitive environment to a small charity which relies heavily on volunteers?

He said: "It's not very different. There are the same decision-making processes, particularly about signing leases.

“The main difference is that at Marks & Spencer I had agents coming to me, whereas when I said 'We are going to open a chain of charity shops' no one was interested at first.

"It's different now. I don't make any phone calls — they all come to me.

"Simply Food was hard work at first, but it got easier. It's the same here. The first shop took a year to open. The second took another year. Then we opened 28 in just three years."

To focus its efforts, the charity joined a study with Surrey University, which looked at how to pick the best locations. The first such academic study of charity shops, it included a demographic analysis of customers, donors and volunteers, as well as footfalls. Surprisingly, Mr Cryer says they ended up targeting similar areas to Marks & Spencer.

And the whole operation is run on professional lines: "We spend a lot of time making the merchandise look good. It's not just put on the shelves," he said.

The shops are "light, bright and airy", mirroring the feel of the children's hospice. Ironically, the recession has created new opportunities, as well as bringing down rents. The Headington branch is large enough to be one of the few charity shops to stock furniture, carefully chosen and artfully displayed.

"If we have space above, it comes at a cheaper rate and we always put in a bookshop."

The bookshops have luxurious-looking chairs, but they only cost £49. "The idea is to make things look smart and professional without spending a lot of money," he said.

Now he is taking advantage of the downturn by taking temporary leases when premises next door to existing shops become vacant — for instance in Carterton, which now stocks furniture.

Surprisingly, he says decision-making at Marks & Spencer was bureaucratic, and had to be streamlined to take fast decisions on Simply Food leases.

He copied the idea at Helen and Douglas House, suggesting a sub-committee to approve new shop openings rapidly.

In one area, he sees big differences in the charity sector, where the watchword is co-operation rather than competition.

"There is much more openness and sharing information. We share ideas with Oxfam, for example."

Mr Cryer is chairman of the Association of Charity Shops, which campaigns on issues such as rogue clothing collectors and Government legislation.

In his spare time, he is chairman of governors of Uffington Primary School, and a member of the shadow board of Cogges Farm Museum, while gearing himself up for more shop openings, including one to be launched in Summertown, Oxford, in July.