All valves working correct and no split hoses, that was one of the first things i checked, as i said, i used a clear bowl in line fuel filter and monitored the fuel levels, it was a hunch that the diapraghm in the main fuel filter was allowing air through but by passed and ruled it out.
Scramble, im leaning towards your way of thinking as it sounds plausable, other than back to the injector issue most other avenues have been explored,
Whats more anoying is i bet my bollox its something or nothing.
Cheers for the replys so far lads Its good to try and talk it through with somebody