The Foreign Office has appealed to Britons retiring abroad to think through the realities of their move.
Not everything lives up to the brochure
Their warning came as the BBC revealed unique data on the scale of Britons moving overseas, many of them people approaching retirement.
British officials in Spain are devoting more and more time to elderly Britons who cannot manage alone.
Many of those who come for help have neither learnt Spanish nor learnt about how the welfare system works.
Bruce McIntyre, British Consul in Malaga, said his staff were often dealing with the cases of people who had started their retirements 15 years previously - but found themselves in desperate situations as they got older.
"Sometimes a partner has died and the other is too old or infirm to go out and buy food," said Mr McIntyre.
"Sometimes people have made bad property investments or have not budgeted their pensions sufficiently and are living in extreme poverty.
"British retirees need to realise that not many European countries have welfare provisions like the UK - there are often no old people's homes, no district nursing, community care or meals on wheels.
"We provide help where we can but there are just a few steps you can take to ensure that it doesn't come to this."
Spanish officials have been increasingly concerned in recent years at the failure of many British citizens to properly register on settling in the country.
According to data compiled by the Institute for Public Policy Research' Brits Abroad project, published on the BBC News website, there are at least 761,000 Britons living in Spain - a number that approaches one million when those with second homes are included. Many of these people are middle-aged, semi-retired or retired.
Pensioners in crisis
In two recent cases, British officials in Spain found elderly expats in appalling conditions because neither had planned for the worst.
In the first case, a 73-year-old woman who had lived in Andalucia since the 1980s found herself helpless after the death of her husband.
She had no family or friends locally and didn't speak any Spanish. Because she had left household finances to her husband, she was oblivious as to whether she was entitled to any local benefits. When British officials heard of her case, she was found living in "abject poverty having not eaten for many weeks, and in urgent need of medical care", said a Foreign Office spokesman.
In the second case, a 74-year-old man who had retired to Malaga became so infirm from arthritis had could not leave his home. The man did not speak Spanish and he had no contact with local social services, community care organisations or his Spanish neighbours.
A spokesman said: "We found him in despair, a proud man living with an untreated but agonisingly painful condition, in utter squalor with no food, no electricity and no idea where to turn."
The Foreign Office's Know Before You Go campaign aims to warn departing ex-pats to put the right steps in place to ensure a happy life abroad. Find out more from the link box in this story or by following the internet link on the right hand side of the page.