An understanding of the behaviour of the plasma edge and divertor physics is essential for the design of next-step machines such as ITER, for which JET with its ITER-Like Wall (ILW) of Be in the main chamber and W in the divertor is ideally suited. The fuel and edge impurities affect the power balance, this determining the power reaching the divertor target plates, which are limited by the mechanical and thermal properties of the plates. A recent comparison of L-mode discharges run during the present JET-ILW campaign and previous JET-C campaigns, in which the plasma-facing surfaces were predominately C, have consistently shown a shortfall in the radiated power calculated from EDGE2D/EIRENE simulations below that measured by bolometry. In order to understand this discrepancy, the contributions to the divertor radiated power as predicted by the simulations have been quantified and the results compared with measurements from a recently upgraded poloidally scanning VUV/visible spectrometer.