As regards the engine I have to say yours does run like a sowing machine Chris. Mine was never sweet, but always went well. Having bent the crankshaft I had to rebuild mine and I've flukely done a good job of the bottom end. It's silent, maintains good oil pressure, never runs hot and thankfully doesn't leak.
The head on the other hand.....I thought it was all simple but I managed to balls up the tappets and now it's noisy and rattly. Still goes ok, but not as well as it should. Sensible option is to find another head, but I'm determined to overhaul the tappets and make this one right