An experimental study on the poloidal mode number (m) spectrum produced by a single toroidal mode number (n) Neoclassical Tearing Mode in JET tokamak is presented, Clear evidence of the existence of more than one significant m components is given. The analysis is performed comparing several methods and diagnostics; among the latter we mention high frequency magnetic pick up coils and Electron Cyclotron Emission radiometer, which measures detailed electron temperature radial profiles at high time resolution. The two diagnostics are also used together in a cross coherence calculation technique. The issue of the interaction of this multiple m structure with the plasma is addressed as well, with particular attention paid to plasma toroidal rotation and rotation shear, obtained from Charge Exchange Spectroscopy data. This effect has been studied under different operational plasma scenarios on JET in order to investigate both dependencies on plasma parameters, and consequences on the scenario itself.