Caught up with a mate last night, he is a mechanic at the local Nissan dealership.
They don't get to work on Patrols any more as most are a few years old and never get taken in for warrantee and services etc.
Showed him the slave cylinder and was amazed by the design, he did not know of the problem and had not heard anyone talk about it.
He was going to ask around and get back to me.
His dad is also a mechanic, although this was new to him, he said with something like this you compress the pistons together as Pearcy said then pump the pedal and hold it down hard to pressurise the system, release the bleeder and the force of fluid rushing in swirls the fluid and air out get "most" of the air. He had not done it but that was his solution.
Bugger of a thing