* Climate scientists say heatwaves more frequent and more intense
* Hundreds of deaths attributed to the heat in Portugal
* Britain braced for hottest day on record
* Temperatures reached 45.7C in Spain in recent days (Adds Mijas blaze now under control, more details from Portugal)
By Guillermo Martinez
JERTE, Spain July 17 (Reuters) - Authorities across southern Europe battled on Sunday to control huge wildfires in countries including Spain, Greece and France, with hundreds of deaths blamed on soaring temperatures that scientists say are consistent with climate change.
In Spain, helicopters dropped water on the flames as heat above 40 Celsius (104 Fahrenheit) and often mountainous terrain made the job harder for firefighters.
Shocked residents watching thick plumes of smoke rising above the central western Jerte valley said the heat was making their previously green and cool home more like Spain's semi-arid south.
"Climate change affects everyone," said resident Miguel Angel Tamayo.
A study published in June in the journal 'Environmental Research: Climate' concluded it was highly probable that climate change was making heatwaves worse.
More than 1,000 deaths have been attributed to the nearly week-long heatwave in Portugal and Spain so far. Temperatures in Spain have reached as high as 45.7C (114F).
Spain's weather agency issued temperature warnings for Sunday, with highs of 42 Celsius (108 Fahrenheit) forecast in Aragon, Navarra and La Rioja, in the north. It said the heatwave would end on Monday, but warned temperatures would remain "abnormally high".
Fires were raging in several other regions including Castille and Leon in central Spain and Galicia in the north on Sunday afternoon. Firefighters stabilised a blaze in Mijas, in Malaga province, and said evacuated people could return home.
British pensioners William and Ellen McCurdy had fled for safety with other evacuees in a local sport centre from their home on Saturday as the fire approached.
"It was very fast .... I didn’t take it too seriously. I thought they had it under control and I was quite surprised when it seemed to be moving in our direction," William, 68, told Reuters.
In France, wildfires have now spread over 11,000 hectares (27,000 acres) in the southwestern region of Gironde, and more than 14,000 people have been evacuated, regional authorities said on Sunday afternoon.
More than 1,200 firefighters were trying to control the blazes, the authorities said in a statement.
France issued red alerts, the highest possible, for several regions, with residents urged "to be extremely vigilant".