Neutron reflectivity was used to obtain spatial distributions within [Os(bipy)2(PVP)3.3(PS)6.7Cl]+ modified Au electrodes (where PVP represents poly(4-vinylpyridine) and PS represents polystyrene) in contact with increasing concentrations of two types of electrolyte, perchlorate and p-toluenesulfonate. Film swelling and corresponding solvent ingress were observed to be more pronounced in p-toluenesulfonate media than in perchlorate media, yet the effects were found to be of lesser magnitude than for the corresponding homopolymer system, [Os(bipy)2(PVP)10Cl]+. Film structural changes upon immersion in solvent and redox cycling in electrolyte were determined. A comparison with the film maintained in OsII and OsIII oxidation states revealed further film swelling in the oxidized state.