If I were you I would get somebody in to do your cooker properly, you obviously have no idea how dangerous both your installation and more importantly lpg is, its incredibly explosive.... far more than natural gas and has other requirements that you wont know about either.My superser has the gas bottle inside it!
Also installed my own lpg gas cooker and would be the first to admit Im not competent but hey ho no can stop me. I used 10mm soft drawn copper for the 10m pipe run to the gas bottle and connected inside the house using some rubber hose I had lying around and stuck this over the end of the copper.
Works fine and cost me nothing as the bits were lying around to hand.