Two new A-site ordered perovskite structure oxides, CaCu3Fe4O12 and LaCu3Fe4O12, were recently synthesized under high-pressure and high-temperature conditions in Kyoto. These compounds contain unusually high valence states of iron: Fe4+ in CaCu3Fe4O12 and Fe3.75+ in LaCu3Fe4O12. Instabilities of the high oxidation states at low temperatures are resolved in CaCu3Fe4O12 by a charge disproportionation transition and in LaCu3Fe4O12 by charge transfer between A-site Cu and B-site Fe ions. Subsequent high pressure Mossbauer spectroscopy experiments have revealed a wealth of further electronic transformations. To understand these electronic behaviours, structural and magnetic studies by neutron diffraction under pressure are essential, in particular to determine the charge distribution and any charge ordering from accurate metal-oxygen bond lengths.