Experimental M-shell nickel spectra in the 14.4-16.5nm region from the JET tokamak (both on divertor and limiter configurations) and from the reversed field pinch RFX have been simulated. These spectra include lines from five ionisation states, namely from Ni10+ K-like to Ni13+ P-like ions. For the Jet limiter configuration the spectrum upper upper limit was higher (18.0nm) and lines from Ni14+ Si-like ions were also observed Collisional Radiative (CR) models have been built for these six Ni ions, considering electron collisional excitation and radiative decay as the populating processes of the excited states. These models give photon emission coefficients (PECs) for the emitted lines at electron density (ne) and temperature (Te) values corresponding to the experimental situations. Impurity modelling is performed using a 1-D impurity transport code, calculating the steady state radial distribution of the Ni ions. The Ni line brightnesses are evaluated in a post-processing subroutine and simulated spectra are obtained. The partial spectra corresponding to a single ionisation degree, in absence of blendings, depend only of the Te and ne values in the emitting shells of the ionisation states considered. On the other hand, the superposition of the these spectra depends on the experimental conditions, as a consequence of the fact that the ion charge distribution depends not only on the radial profiles of Te and ne, but also on the chosen ionisation and recombination rate coefficients and on the radial profiles of the impurity transport coefficients in the region of the emitting shells. For each experimental spectrum a few simulations are presented, since a unique choice has not been found by selecting the input parameters of the transport code. Since the aim of the paper is an investigation of the atomic physics of the M-shell ions, this section on the plasma physics phenomena is purposely quite limited. Various simulations are, nevertheless, necessary to determine the electron density and temperature values in the emitting shells and to show the influence of line blendings on the single ionisation degree spectra. The single ionisation degree spectra are then compared with the predictions. For the considered ne range the PECs can be considered independent of ne. There is a their Te dependence, but it is much reduced when considering line ratios and the spectral fits done are actually a comparison of line ratios. The global agreement found between experimental and simulated single ionisation degree spectra give confidence on the atomic data used to build the required CR models.