Quite frankly I'm fed up with it now, got the new 36mm ring, checked end gap, adjusted it, installed it, rebuilt the car and then still won't start, not even a cough and splutter.
I'm not sure if I damaged the head beyond starting when I tried to install the piston with the new ring into the head wrongly, didn't realise there was a centering pin on the intake side before rebuilding it so got a bit forceful at one point and scored the head.
I might stick the old ring back in and see if it will start, if it does it's just down to the new ring. It didn't have any issues before I replaced it.