Thanks Ped, (without your info would not have even thought to use the 13xx part.)

OK so I sorted it, I read on a US forum that you can at a pinch use a 4x2 oring in place of the quad, I did it works very well !
It is tighter on the spigot, but as Ped eluded to this oring is tighter so issue gone..with this spigot LOL

I used the spring from the 13xx as well as there is more volume in the valve now (longer internal dia : ) so old spring to short.
Made custom pin to hold valve in place and JUST kept the rear oring out of the hole, keeping seal

GUN IS FINISHED phewwwww