Metallic films show a transition region in the mesoscopic regime between atomically thin and macroscopically thick films. In this regime the Coulomb interactions between the electrons in the film is increased and therefore the material properties of the films must be described by a non-local permittivity which takes this effect into account. An analytical model that can describe these non-local properties is the Keldysh-Rytova model. We investigate the influence of non-locality in these so-called transdimensional films on the near-field heat transport, on thermal radiation and on various optical phenomena such as the Goos-Hänchen effect.