It may be that very British obsession with class, deference or a prurient interest in the lives of others. Perhaps it is just the sumptuous costumes and sepia-tinged nostalgia for a bygone age when the brasses shone and the linen sheets were crisply ironed.

But whatever the reason for the surprise success of ITV's hit period costume drama Downton Abbey, Julian Fellowes' Sunday night serial has reignited interest in the goings-on below stairs for millions of television viewers.

It is a life that has changed dramatically since the Edwardian high-water mark, when upper and upper middle class households employed more women than any other industry in Britain. Today the tens of thousands that make their living – officially or unofficially – cooking, cleaning, driving or keeping house for others are more likely to come from overseas and work for ex-pat families than from our own homegrown working class.

They are also subject to the same rigours of professionalism and cost control as in any other workplace, despite the wealth and often glamorous lifestyles of their employers.

Laura Harrall, of Greycoat Placements, which specialises in finding situations for high-calibre domestic staff, admitted that although the industry had been transformed since the days of Downton Abbey it still made for compulsive viewing. A former housekeeper, Ms Harrall said it took a certain kind of person to meet the challenge of 21st-century domestic service – where the economic downturn has resulted in hired help being required to turn their hands to an increasing number of tasks in what can often be a claustrophobic environment.

"It's not all starched and stuffiness as it used to be," she said. "But it is not an easy job. It is a very good profession for people who like to work for others; to work to very high standards and to make sure someone else's life runs smoothly," she said.

Whereas once domestic positions would be passed down through families, today's recruits are more likely to be trained in the world's leading hotels and hospitality industries. And for the very best, the rewards can be highly attractive.

The most sought-after couples who between them fulfil the roles of cook, chauffeur, butler, housekeeper, gardener and handyman are increasingly in demand and can earn anything up to £60,000 a year. Accommodation – normally self-contained and more often than not in the ritziest parts of town and country – is thrown in, as is travel, food, heating and other bills.

But in return, employees are expected to work very long hours, finding themselves at their employer's beck and call from morning until night six or seven days a week. Staff must be able to put a distance between themselves and their masters.

"The houses are very nice but in the end you work there – you don't own it. That is very important to remember. People think they can go and work in a large property and almost acquire the lifestyle of the person they are working for," said Ms Harrall.

"You do get more personality clashes than if you put people in an office job. You are working in someone's home. In an office if you don't get along with an employee you can say goodbye to them at five o'clock," she added.

Francine Bray, founder and managing director of Chelsea Staff Bureau International, said recent years had witnessed a profound power shift in relations between domestic staff and their employers.

"The employees have the whip hand. If it is too much one way or the other then it is no good. In the old days they were like slaves – they belonged to their masters. Today they are not – the master belongs to them. They do dictate. One of these days they will have a union," she said.

In return, she added, old-fashioned notions of duty and responsibility have been swept under the carpet. Few employers are now prepared to put up with a member of staff with children or a pet. However, Ms Bray, who counts some of the world's richest people and most famous celebrities among her clients, believes there is little to suggest the old days were as romantic as television might have it.

Finding the right people, she said, was also increasingly problematic. "Even the last four years it has become almost impossible. That is why we are starting a school for butlers, couples and nannies. They are very, very long hours. The employer wants to get as much for their money as they can. The other [employee] wants to do a minimum for their money. It's a tug of war. It is not a happy world because the domestic household staff really hate doing it but they make a lot of money."

Perhaps unsurprisingly in the face of such tensions, many employers new to the business of hiring live-in domestic help can find the process daunting – although in the end choosing the right staff is a matter of instinct as much as anything. "It doesn't have to be scary. It can be a stressful time. They are inviting practical strangers to come into their homes five days a week," said Ms Harrall.

"I talk about their expectations and try and find a suitable match. There will always be a formal interview and sometimes a trial but they will often have gut instincts whether you get on. They will normally make a decision based on personality rather than qualifications."

Raffaele Riviezzo: 'You give your life to these people'

Starting his career in hotels aged just 14, Mr Riviezzo was invited to join the household of Italy's famous Innocenti family – creators of the Lambretta scooter. He also served for eight years with the fashion designer Valentino and later worked for a branch of the Morattis, owners of Inter Milan. He is currently working temporarily for an American employer in London. His teenage son and daughter live in Rome. He speaks French, English and Italian.

Mr Riviezzo, 49, said: "You have to be flexible and be able to do everything. You give your life to these people. I work a minimum of 13-14 hours a day, every day. This is my first day off in 10 days. It is the type of job that is really hard. I get perhaps £700 a week. I wake up at 6.30am and I go by myself to prepare breakfast for 8.30am.

At 12.30pm there is lunch and at 7.30pm it is a drink with some different appetisers every day. Then at 8.30pm it is dinner. I do the shopping and I cook Italian food. When I finish I go to bed. I have just one housekeeper. She is here for eight hours and the rest of the day I am alone.

Before it was different. I was a manager in big households with a lot of staff under me. There were houses all over the world – in London, St Moritz, New York, Rio de Janeiro.