A controlled investigation of light-induced changes in hybrid perovskites is required to achieve stable operation of tandem solar cells and colour-tuneable light-emitting diodes. Recent reports have observed light-induced shifts in the optical bandgap under illumination with visible light, for which the origin is not understood, but thought to be partially due to halide ion migration. We propose to use muon spectroscopy to explore changes in the local structure of the lead-halide pervoskites, CH3NH3Pb(IxBr1-x)3 on illumination. Experiments will focus on samples continuously irradiated and compare the results with those made in dark conditions. Temperature dependent measurements will allow for the carrier lifetime and diffusion rates to be calculated. Preliminary measurements exploring the dynamics of the structural change will also be explored.