A Hamiltonian guiding centre particle following code has been developed to study the fast particle motion in the presence of arbitrary time dependent electromagnetic perturbations. In conjunction with an MHD stability code, this code was used to analyse TAE/KTAE induced alpha orbit diffusion and alpha losses in JET plasmas. Resonant alpha orbits are studied below and above the stochasticity thresholds, in the presence of single or several TAEs and KTAEs. Monte Carlo randomized ensembles of alpha particles in the presence of finite amplitude TAE/KTAEs are followed and estimates for the stochastic diffusion coefficients are obtained. Generalization of the method towards the self-consistent wave-particle evolution is described