Good news - the panels are done, just have to pay and get them shipped back to me for re-assembly
In the meantime i've been doing some testing on the bench.It all runs fine with no leaks, but the shots i was getting weren't great with a big divot in the puck everytime, always in the same place.As a result the shots were usually channeling thru the divot.it was abit frustrating trying to figure it out, tried re-positioning shower screen, no luck.Eventually removed whole piston assembly and figured out one of the holes in the piston was aligned directly with the water inlet hole in the cylinder bore.(the piston has holes to allow water flow and to 'energise' the seals.As the seal went past the inlet hole, a jet of water must have been spraying down thru the hole and destroying the puck.I added a small teflon washer above the piston, thereby aligning the holes differently when the piston was re-assembled.The results were instantly improved, much better shots and no big divots in the puck;

For anyone working on this group, the piston seals are not standard to any other group, i had some custom made.The seal code is SU27 (2.125" OD x 1.5" ID) they come standard at around 8.5mm thick but i had them made at 7.5mm thick to better suit the piston grooves.
Grouphead seal is 72 x 58 x 7mm thick, an odd one i found at cafe parts
Valve tap seals are same as Unic tap seals 16 x 4 x 5mm thick
Hope to bring you all some finished (mostly) shots in a week or so