A gas cooker bayonet fitting is a gas fitting and as such the gas regulations apply - period. If you think that because its possible for anybody to uncouple and recouple it that makes it ok to do so, you are mistaken. The actual intention of the flexible hose is so that the cooker can be carefully moved out so that cleaning can take place without disconnecting the appliance. The bayonet connection allows the hose to swivel on the O ring.The gas regs are there to save lives not line corgi fitters pockets. A cooker is an unflued gas appliance siting, ventilation and correct working of the appliance, operation of the safety devices all need to be checked plus a stability bracket. NEW as well a second hand appliances can leak I've had them all. Plus the correct positioning of the back plate elbow to allow the hose to hang correctly is vital.(far too many registered installers dont do this either ,) Its very rare one out of fifty ? where the backplate dose'nt need moving so pipework is usually involved. A gas fitter would have to pay £300 or so to be assessed as competent to work on or install cookers! As for transco checking your work- if its classed as immediately dangerous and you in your ignorance have fitted it CORGI and the HSE will be after you. Make no mistake illegal and incompetant gas fitters are been jailed. On this occasion you are not never wrong but just plain wrong.