Hi Mark,
What is the army registration number of your Fox? I may have some info on it.
Noisy power steering suggests it needs bleeding, air in the system can make some funny noises. Check the fluid level, this is the little black tank behind the gunners seat, there is a dip stick in the cap.
To bleed the system you need to lift the front wheels off the ground, start the engine and operate the steering wheel from lock to lock with the bleed nipple on the steering column open.
I hope this helps,
Chris