OK Heres an update a week later.
The surging problem is gone, it now will run consistantly.
Flying it today it seems anemic, like its going fast, but not flat out, uplines have no where near the pull they did. Takeoff was sluggish, like only about 3/4 throttle in the climb out.
Setting the high end doesnt seem anywhere near as powerful or distinct a peak RPM as previous testing, it just starts to die after peak.
Mixture (needle valve) is set to about 1/4 rich of peak, idle is great, pick up from idle is smooth and quick with no spluttering etc. After starting I open the throttle wide then back to idle, take the glo power off and NO change or very slight drop in RPM, pinching the line quickly at idle gives a very slight increase in RPM. WOT and hold the plane vertical and no change or very slight increase in RPM.
Compression 'seems' to be as good as it was after the run-in period, maybe better.

Any ideas people ?