well theres not much to it,havent done my other cinq yet as ive actually got to get the car road legal for now.got a set of vectra twin horns waiting to go on. just get cavvy or vectra twin horns and they work a treat.
i would also recommend relocating the horns to the engine bay ala turbo cinq.bolt it to the gearbox engine mount bracket to get the horn out off the spray