Oxide ion conductors are key components in a number of technologically important applications. Our research programme on the development of new oxide ion conductors, using neutron scattering methods in conjunction with computational modelling, has resulted in new insight into the relationships between structure, dynamics and properties in some of the leading solid electrolytes. Crucially, we have been able to demonstrate the importance of variable coordination environments of cations and the rotational freedom of these polyhedra in facilitating high oxide ion mobility at low temperatures. We have recently prepared new excellent oxide ion conductors based on the brownmillerite Sr2ScGaO5. They have a disordered local structure and we therefore request 3 days of POLARIS beamtime for neutron total scattering experiments on the new materials to elucidate structure-property relationships.