High-pressure ices III and V each have quite small stability fields; consequently, their physical properties, in particular the P- and T-dependences, are poorly determined. We propose to use a novel technique to synthesise these ice phases in a pressure cell under Ar gas (which avoids formation of hydrates by penetration of He or Ne into ice Ih) and then to switch to using He gas. Helium will not dissolve in the high-pressure phases, and restores our capability to cool the specimen as low as 50 K at 5.5 kbar without condensing our pressure medium (Ar freezes at 190 K at 5.5 kbar). In this way, we will be able to measure the thermal expansion of ice V over a large range in T, and measure its incompressibility on decompression to 1 bar at 50 K.We propose also to commission a new piston-cylinder cell using ice V as a test specimen, examining the order-disorder transition in DCl doped ice.