Well, we have the same problem in California (U.S.A.)
they are raising the price for water again and limiting our water to 4200gal. per Mo. Conserve, Conserve, I live in the Mojave Desert
where temps get to 118*degrees , we go by Farenheit I think you go by Celsius. One of the better ways is a "Swamp Cooler" where the water trickles down over pads with a fan in it to cool the air. It does not use much water. Keep the home closed all morning till it gets hot and start with fans. An attic fan helps cool the home by taking the super hot attic air and getting rid of it right away. Believe me I know what Hot is. I even work outside in those high temperatures. Straw hat, sunglasses, a wet towel hanging from under my hat over my neck, gloves, long sleeves, Levis and boots. Yea what fun. Time to go to work see ya.