Well boiling and blowing out with airline didn't cure it

Removed carb again and made two new base gaskets, refitted the carb and still no improvement
As a long shot i removed the jet with the large flat head from the side of the carb and replaced the O-Ring with a copper washer and low and behold it is a different engine now
It now ticks over nicely and the idle mixture screw does have a effeect on the running
Snap the throttle open and it picks up nicely
Hold the throttle mid position and it seems to be misfiring

Seems like a bit more playing about is in order