Most A320 main components are manufactured in France, Spain, the UK, and Germany. Airbus transports them via Beluga to Toulouse where they are held prior to entering the final assembly hall. Airbus runs an astoundingly efficent operation using the "just in time" technique of delivering components just prior to assembly, that pervades manufacturing these days. These components for the most part arrive pre-wired with harnesses and cabling, expediting the final assembly.