SHE'S ALIVE!!!!!!!!!!!
The stoooopid thing is i dont even know what was up exactly! I pulled everything back out of the fuse box and plumbed it all into the original (which is identical). turned the key, still no prime but i noticed when cranking the fuel pump was running?? i kept lettting her crank to get the fuel pressure up (as i had dismantled the system so would have been empty) and low and behold she fired up with no fuss. I then found the relay which was originally on the car (which isnt a vw item) and this time she primed properly and started perfectly....
Thanks guys for your help so far and RJ you're a legend and you know it.
I still have a way to go though, i want to see if swapping fuse boxes was a fluke, i think there was just a few crap connections as suggested by kraM. so i want to try with new box as its better condition. funny how the pump relay from the replacement fusebox didnt prime but again could have been a bad connection at the time.
I have quite a few other things to tackle now, i know the cold start valve isnt connected and has nowhere to go yet which is odd, and obvioulsy i have nothing else wired in yet.
thanks again everybody.