We propose to use OSIRIS to investigate the changes in magnetic ordering which occur when a series of layered oxysulfides with mixed-valent Mn ions in their oxide layers are oxidised by the deintercalation of Cu from their sulfide layers. These systems complement the mixed-valent Mn oxides and also show a range of magnetic structures which we expect to be able to modify by oxidation. Complex magnetic structures are anticipated which require the long d-spacing capability of OSIRIS. This accompanies an experiment on POLARIS which will correlate the structural chemistry of these systems with composition.