Sam, the regulator sits just behind the main accumulator sphere (in fact the sphere screws into it) low down on the engine by the front of the gearbox. The tick can be quite soft and hard to hear above the idling of teh engine, particularly a diesel.
Another way is to listen to the pump via a stethopscope which can be either a fancy engineers one or a long screwdriver or even a length of wooden dowel. Place one end on the body of the pump (take care of rotating pulleys and belts!) and the other against your ear. When the pump is idling because the system is up to pressure it'll be more or less silent. When it's actively pumping it will make a rapid machine-gun sort of noise - best way I can describe it- sorry!
So, listening to the pump with a stethoscope you should hear lots of silence interspersed with regular bursts of the machine-gun fire. The silences should be at intervals greater than 30 seconds and the bursts of fire should last three to five seconds as the pump works to restore pressure; the bursts of machine-gun fire are equivalent to the regulator ticks I spoke of earlier.
If you hear more machine-gun fire than silence then assume the accumulator sphere is flat (in need of replacement) or there's an internal leak in the system causing a loss of pressure... The latter is rare but the former is quite common.
Hope that all makes sense Sam. I'd love to see the looks on people's faces as you listen to the hydraulics with a stethoscope - you can always say you're checking its pulse and in a way you are
