Two different methods for localising low-order rational q locations in the JET tokamak have been developed. Both are based on the radial localisation of magnetic islands, which corresponds to rational q = m/n values resonating with the island helicity. The island toroidal mode number n is determined without any ambiguity by a toroidal array of Mirnov coils while, since poloidal information in Mirnov coils is corrupted by plasma shape effects, the poloidal mode number m is inferred with the aid of preliminary raw information on the q profile from equilibrium reconstruction. These mode-localisation techniques are particularly useful in high-beta advanced tokamak scenarios, in which Neoclassical Tearing Modes (NTMs) driven by density and temperature gradient perturbations are very frequently observed. In this paper both methods will be presented and their results will be compared.