Yes thats what im thinking. I use a Polarbrite analogue flow controller so im not sure its got a pressure sensing facility so might need the pressure switch.
Im actually considering just using the pump with an on/off switch, doing away with the flow controller and adding a waterflow bypass to the tank.
At first I was wary of doing this as the pump will be constantly running until switched off but i've just read somewhere that when using a pressure switch with the shurflo it draws twice as much current from the battery to start the pump as it does when its actually running.
So it probably wouldnt use any more juice from the battery as it would with the pressure switch cycling the pump on and off.
I use a high flow anyway with a flow control valve on the pole hose to stop water flow between windows so this might be the option i'll go with.