Edge plasma parameters influence plasma performance in many different ways (profile stiffness is probably one of the best known examples). In ELMy H-mode, a thin region with improved transport characteristics (Edge Transport Barrier) links the core and the scrape-off layer. There is a strong coupling between these three areas, so that even a modest variation of plasma parameters in one region can lead to a dramatic change in the overall plasma performance. Systematic MHD stability analysis and self-consistent integrated predictive modelling of a series of JET ELMy H-mode plasmas, including scans in gas fuelling and triangularity is presented. The main conclusion is that indeed plasma performance depends sensitively on the edge plasma parameters, which should be modelled in a self-consistent way.