Halide perovskites have been the focus of an intense research effort, ever since the discovery that they can be employed to fabricate highly efficient solar cells. One of the key challenges is to produce materials that are chemically and structurally stable, yet have optimal optoelectronic properties. This effort is hampered by the almost complete lack of experimental data about their basic thermodynamic behaviour as a function of pressure and temperature - the ‘classic’ clean variables through which stability is tuned. Here we propose a neutron powder diffraction study as a function of pressure and temperature of the ‘fully-inorganic’ CsPb(IxBr1-x)3 perovskite - a promising alternative to the popular organic-inorganic ‘hybrids’. Key information obtained in this experiment will be later compared with first-principle calculations to define a route towards better materials properties.