Thanks for all of your input guys, its been a great help! Its been an eventful weekend with lots of swearing etc, but i can safely say that i have managed to get it running now!! The shaft of the pump was in the wrong position when it can back from being overhauled, so turning it through the best part of 270 degrees, to its position before 12 oclock has done the trick.
My woodruff key is very shallow in comparison to others ive seen, and like a numpty i thought i was in the right position. I've given myself a talking to, and now it starts on the button every time now!
The vehicle hasnt run for around 5 years or so, and on start up it sound a bit knocky.....so im hoping its just bad lubrication, and a good oil change will see it right? It was absolutely fine before i parked it....apart from the pump, so im hoping to give it a new lease of life!
Thanks again guys for your help!