When you live in a holiday resort like Marbella, you get used to watching an endless stream of holidaymakers with the last-day blues, solemnly wheeling their suitcases past the swimming pool, taking in a last view of the sea, before embarking on that dreaded journey to the airport.

"I hate this moment," sighs Mary Foster from Bristol as she hauls her bags out of her seaview apartment on Marbella's Golden Mile. "It's always such a horrible feeling having to leave all of this," she says, wistfully casting an eye across the palm trees.

Mary only has six weeks to go though before she comes back again. Apart from other obvious benefits such as being able to escape when the black skies of August at home look disturbingly like winter, owning a bolthole in Spain is a great way to avoid that awful final-day-of-holiday feeling that you'll never return.

Along with some 600,000 British buyers so far, with a further half a million predicted to do so in the next five years - Mary has bought a holiday home in Spain which she visits several times a year, sometimes for as long as six weeks each time, and with different combinations of friends, offspring, grandchildren or on her own.

"We can get here so cheaply and easily on low-cost flights that we can come out here regularly," says Mary. "And each time we come we bump into lots of people we know who are doing the same thing, so you end up with a whole new set of friends in a different country."

Shaun Powell, managing director of Lighthouse, a company which finds holiday homes for foreign buyers by working with a network of ethical estate agents in Spain, comments: "In the past, we went en masse to Spain to spend our annual cheap fortnight in the sun. Now we are still going there in equally large numbers but as home-owners not package tourists. "Spain is by far the number one destination for British second-home buyers," Powell adds, "and two thirds of them choose to buy on the Costa del Sol or Costa Blanca because these coasts have an excellent year-round climate, good infrastructure and established expat communities."

Sometimes, however, a lack of local knowledge and expertise in buying property in a country with a different culture, language and legal system can see buyers falling foul of disreputable agents, developers or negligent lawyers for whom sudden price changes, selling illegal properties or promising unrealistic returns on off-plan investments are daily practices.

This is why Lighthouse was set up, to provide its customers with a protected environment in which they can be reassured that they are dealing only with trustworthy parties.

"Our network of 100 agents currently spans the Costa del Sol and Costa Blanca, with Almeria, Mallorca and Costa de La Luz to follow," says Shaun Powell.

"All of our member agents must work according to the network's strictly-enforced code of ethics, rules and regulations. If they don't, they are expelled from the network, which is highly damaging to their business, and there is an arbitration process to resolve matters for the customer," Powell adds.

Holiday homes need not only be by the beach, of course. Lighthouse has a database of nearly 10,000 properties, which range from rustic 30,000-euro ruins to 15-million euro villas, and many customers express an interest in buying an inland property in need of renovation.

Tomás Mazón, Professor in the Sociology of Tourism at Alicante University who is researching the impact of residential tourism in the Alicante province, says: "There is a shift inland among foreign second home buyers who want to live in small, less developed villages with a higher quality of life, but which are well connected to the coast by motorways."

As part of his research, Mazón recently interviewed 1,000 foreign home owners who spend at least six months a year in the province; 93% said they came for the climate while 64% said they enjoy a better quality of life in Spain than in their own country. Most had visited the area for years as tourists before buying.

"The whole of the Costa Blanca from Denia to Torrevieja is seeing the phenomenon of foreign buyers, and second-line towns such as Rojales and San Miguel de Salinas are seeing frenetic activity - as are almost all of the villages in the Bajo Segura area where there are plans to build 160,000 tourist homes and nine new golf courses," says Mazón.

Shaun Powell agrees that buyers are increasingly looking to cheaper areas in the East of Spain. "The average property price on the Costa del Sol is 300,000 euros as prices there have risen considerably over the past few years, so many buyers are either starting to look inland or are considering areas where you can buy more for your money such as southern Costa Blanca around Murcia, and Almeria where there is still a wide range of options for 100,000 euros. And you have the added benefit of being able to rent out the property to cover your mortgage," he says.

Despite rising property prices in Spain due to high demand from foreign buyers, an unprecedented number of British people can now afford a holiday home overseas, Powell claims. "We estimate that buying a home abroad is now financially feasible for five million British people, which would have been unimaginable 10 years ago.

"Many people release equity from their UK properties or benefit from higher disposable income or inheritance sums to invest in a Spanish property."

Tony Gatehouse, Chairman of Medsea Estates, one of the largest estate agents in Costa Blanca and the only AIM-listed property company, has worked in real estate on the coast for 20 years and reports that residential tourist numbers are now booming.

"In the next decade, about 2.3 million British people over 50 will retire abroad and the vast majority will choose Spain," says Gatehouse, who comments that alongside the constant demand among those planning their retirement, there is a growing trend for younger people to live and work in Spain, which is opening up new areas of interest. "We are seeing increasing demand away from our original market around Torrevieja in favour of the north, towards Valencia, and south around Murcia."

So, bear all this in mind next time you are forlornly packing your bags and preparing to say goodbye to Spain. Remember, it doesn't have to be adiós…