The linear stability of ideal instabilities with low toroidal mode numbers has been assessed for various high-beta plasmas in JET including steady-state and hybrid scenarios. Results of detailed stability analysis of discharges with the minimum in safety factor near 1, 3/2 and 2 are presented. In all cases, the plasmas are found to become unstable to global ideal kink-ballooning modes as the minimum safety factor decreases with the current diffusion. The plasmas are found to exhibit continuous modes experimentally which degrade performance, with the mode onset being extremely well correlated with the crossing of the numerically predicted stability boundaries. The most favorable profiles for global stability have also been assessed.