I have often read that you cannot connect a hob with a flexible connection under Gas Safe rules and regs. I was also told this by my gas fitter. Just in case you are not aware there is now a way, albeit a "semi-rigid" pipe, but to all intense and purposes it is a flexible. See Screwfix part no 5802V - Tesla Semi Rigid Steel Gas Hob Connector £19.79. Tesla Semi-Rigid Stainless Steel Gas Hob Connector 16mm x 1m DN15 3 Pack