We propose further zero-field muon spin depolarization measurements at temperatures above 300K in order to determine barriers for thermal diffusion of positively charged muonium in ZnO, TiO2, and other transparent conducting oxides. We have found that the Mu+ centre undergoes local quantum tunnelling and a site change, but not extended motion, up to 380K in ZnO and 300K in TiO2. We require access to higher temperatures where the Mu+ centres become diffusively mobile in order to determine the barrier energy for classical thermal motion in selected transparent conducting oxides. Results are directly relevant to hydrogen diffusion in these materials. [Included in the PhD project for Brittany Baker.]