I'm buying a new freestanding gas cooker - do I have to have this fitted by a Corgi installer. I have the bayonet fixing on the wall and the hook that the chain from the cooker will attach to. Can I just by the hose (C2 Kit they used to be called) and fit this to the cooker and plug it in by the bayonet fixing to the wall? If I have to get an installer - how much should I expect to pay roughly?