Last week Doreen Little was sharing a country mansion, complete with swimming pool and tennis court, with a boisterous labrador. Next week she could be feeding the goldfish in a pop star's penthouse flat.

Doreen is a professional 'homesitter' with a flexible approach to domesticity. Every so often she and her husband, Brian, lock up their own modest Bristol semi and - pet tortoises in tow - settle into other people's homes and daily routines. Their task is to provide pet-care and the ultimate 'lived in' look - ie to provide security - while the real owners are on holiday.

In the last three years Doreen and Brian, who are both in their sixties, have slipped effortlessly into the armchairs of assorted aristocrats, celebrities and VIPs. But this summer their temporary homes include the rather less palatial because one insurance company, set on convincing less affluent holidaymakers to leave their homes occupied, is offering cut-price premiums to policy-holders who employ retired people as homesitters.

The couple's assignments take them all over the country and require them simply to remain in the property for most of the day.

'It isn't a question of actually 'doing' anything,' admits Doreen. 'You cook and clean up after yourself, just as you would at home, and you might feed and exercise pets, but you don't have to clean windows or mow the lawn - most of the houses have staff to do all that.'

Dealing with bizarre requests is, however, part and parcel of the service. 'People do want you to do strange things - especially when it comes to pets. On one house-sit we had to collect our scraps and feed them to the local fox. Every night I had to stand out in the back garden banging away on a tin plate to let him know dinner was ready.'

Doreen is one of the 500 ever-accommodating employees of Homesitters Ltd, an Aylesbury-based company that has been dispatching retired couples to its 3,000 clients for 14 years. Motivated not by financial gain - the job is unpaid, although food and travelling expenses are covered - but by the 'experience', she claims to have found the ideal retirement pastime.

'We get to enjoy beautiful countryside in areas you wouldn't think of holidaying in. And seeing how other people live is fascinating - especially when it comes to the titled folk.

'They lead such different lives to us,' says Doreen, a former doctor's receptionist. 'Some of the grander houses have massive dining tables that are permanently set, all elaborate silver and crystal, and ready for entertaining. I'd be afraid to touch anything.'

When Carolyn Smyth (not her real name) opened her lavish Sussex home to the scrutiny of complete strangers she was apprehensive, despite assurances that her homesitters were doubly insured and had been subjected to rigorous security checks. 'The first time we wanted someone who came from a long way away - we were afraid there would be local gossip about what sort of possessions we had.

'It isn't easy letting others see how you live. It's like handing over your private life to them. One does run around making sure everything is clean and tidy, especially the first time - I looked in my cutlery drawer and nearly had a fit because it was full of crumbs,' she recalls. But now Carolyn and her husband, Tony, who runs a publishing business, are more than happy to entrust their 20-acre country estate, beloved alsatian and four cats to their regular sitters.

'We have used this particular couple four times now and they are just brilliant. It has got to the stage where they walk in as we walk out,' she says.

The Smyths even pay extra for 24-hour cover so that the house is occupied for every single minute of their frequent business trips, exotic holidays and weekend breaks. Sitters can usually leave the property for up to three hours during the day and one hour at night.

'We are vulnerable because the house is very isolated. We have never been broken into and we want to keep it that way. Anyway, we don't really like the thought of our dog being on his own for any length of time.

'It isn't a big price to pay for peace of mind. In fact, it works out cheaper than paying for kennels and a cattery.'

According to Adele Barclay, of Homesitters, many clients are attracted more by the thought of this personalised pet-care than by security considerations. One gentleman went away happy in the knowledge, not that his antiques were in safe hands, but that his precious parrot wouldn't have to forgo her nightly apple crumble and custard.

The cost of such devoted service depends on the type and size of pet. On top of a daily flat rate of pounds 17.35, you can expect to pay around pounds 2.15 a day for a medium-sized dog and 75p for a cat. There is no charge at all for 'undemanding' pets like hamsters or goldfish, while individual quotations are given for 'livestock' - in practice meaning anything from chickens to snakes.

Homesitters are assessed on their pet savvy and unflappability before being accepted on the books. 'Pet skill' ratings prove invaluable when it comes to finding a sitter who can contend with an incontinent Pekingese or a toad needing three walks a day.

'We are rather like a computer dating service, matching up the animal to the homesitter,' explains Adele. 'For instance, if the pet is used to sleeping on the owner's bed, Homesitters will provide someone who doesn't mind sharing a duvet.'

But while homesitters are thoroughly adaptable in other people's homes, some are slightly more reticent when it comes to their own properties.

'The more sits I do, the more I think it is a good idea,' admits Doreen Little. 'But I don't believe I would employ someone myself - even if I had the money.

'To be honest I don't really like the idea of someone wandering round my house. I get upset enough when my sons-in-law come round, do the dishes, and put everything back in the wrong place,' she says.

Homesitters, Buckland Wharf, Buckland, Aylesbury, Bucks HP22 5LQ, 0296-630730.

(Photographs omitted)