the brake system may use the hydraulic system in an assisted mode.
if the brakes are acting up whatever is causing the other problems may be affecting the brakes as well.

i'd start with the pressure test on the main pressure at the hydraulic valve, if thats ok then...
move to the auxillary pressure test... if thats ok then...
go back to the priority valve... it may be clean but how does it move inside its chamber? if it sticks at all and i mean AT ALL when you move it in and out then that most certainly could be the cause.
My other thought is some kind of problem in the auxillary valve circuit, all those functions use the auxillary side of the hydraulic system so its understandable you would be having all these issues.

Hi there
The priority valve was removed and cleaned with no evidence
of debris also the pressure test on the ls line on the steering being move sometimes pressure and sometimes nothing unless another serviced was moved
I gather that the pump on stand by pressure supplies the steering orbital and then when steering being move charges it to system pressure
there is a odd problems with the brake and we are wondering if the main valve is leaking (thus loosing pressure )
JD in england seam to have no idea and looking into system the brakes system is suspect
please help its driving me insane

sure sounds like a priority valve problem or hose connection at the priority valve. when you say "Proirty valve checked" could you describe further how it has been "checked" (did you test pressures at it's connections?, loaded and unloaded?)