Peugeot 206 HDi power steering whine?

My cam belt is whining loudly when the hydraulic pump has demand whilst the engine bay is cold or the vehicle is decellerating. So when steering on medium to full lock in the cold, or when slowing the vehicle by gearing down the belt sounds like it is slipping or the pump is straining? Is this a sign of definite wear of the hydraulic pump or its bearings? or low / cold fluid or something else? If so any idea on the fix please?
Thanks