By Mariano Valladolid and Marcelo Del Pozo SEVILLE, Spain (Reuters) – Fan-sellers were doing good business in the southern city of Seville on Saturday as Spain sizzled in the hottest pre-summer heatwave for at least 20 years. Carriage drivers dampened down horses who take tourists around the historic sights of Seville such as the Real Alcazar Palace and Plaza de Espana. Temperatures reached 40 C (104 Fahrenheit) degrees in the Guadalquivir valley in Seville and the nearby city of Cordoba on Saturday, the national metereological office AEMET said. Temperatures could rise to 42 C (108 Fahrenheit…