It is not just the fact that you plug it in, A twist and a turn yeah simple is'nt it ??? But who is to say that the cooker and its installation is sound. Even a new cooker has to be checked for safety as it could quite easily have been knocked or damaged in transit and even though brand new could be dangerous. The pipes and bayonett may also be dangerous. We do not only just plug in and walk away we check the whole gas installation is sound and safe aswell as checking and certifying the new cooker has been installed and is safe to use. But I agree �100 is real steep I would arrange for an independaent CORGI gasman to fit it and certify the installation as it should only cost you the price of a call out and the registration fees so you should be payuing no more than �50 to �60 depending on whereabouts you live.