OK, so it was a wind up

After setting it up over a few days, I thought I'd get a better bite than that .....
The problem is the hydraulic lifters. I'm guessing here, but I think the people who remanufactured these heads, decided to cheapen out and just put the lifters in a parts cleaner rather than fit new ones.
So far I have stripped out and reassembled 3 of them, the night caught me so the 4th one is stripped out and in the cleaning bath (Ice Cream container supplied by Bruce and pressure pack cans of degreaser from Super Cheap) I bought some air tool oil from the spares place down the road to use as the priming fluid when reassembling them.
Each lifter has left enough black grit in the container to cover the bottom of the 4 ltr plastic ice cream bucket. It takes 4 good blasts with the degreaser to actually find the bottom of the lifter bucket, the bleed hole that the ball bearing seals was blocked in each one so far, as was the oiler hole to the rocker through the top of the lifter .... lucky it's overhead cam, so plenty of oil splash to keep everything lubricated.
I had to crush the lifter in a vice, hitting the vice winder end with a block hammer each 1/4 turn to get the lifter to compress so I could pry the collar off. They claim they can not be serviced because of the locking collar .... well, maybe for American mechanics and those that just know how to remove and replace, but with a bit of effort, the locking collar can be removed and crimped back on once the lifter has been cleaned and assembled.
With a bit of luck, I should have them all cleaned and back in tomorrow ready for a compression test.
Lots easier than taking the heads off

Old mechanics know how diagnose and how to fix stuff, the new breed just seem to know how to get computer scan codes and replace stuff.
Who ever poured all the $$ into this engine and still had issues, would be really p*ssed to find out how simple the fix actually was
T1 Terry