Hi - I have recently fitted a new kitchen and want to continue with a gas hob. I have cut out the work surface and sat the hob into place. The hob is positioned above an electric oven which has already been installed by an electrician. I've been told by a plumber that the hob supply needs to be via copper pipe. The existing copper supply pipe needs extending (it originally fed a free-standing gas cooker) by approx 3 feet - along and up the wall. Am I allowed to extend the existing piping to the hob before a CORGI plumber actually connects it up? Also if I am, how do I empty the supply pipe, from the meter, of gas safely?