Got it all back together this morning and its fine now, good as gold...
When i removed a plug todo comp test last night it wasnt very tight, im wondering if that caused the tapping in the same way a blown exhaust manifold gasket does. Looking at it this morning it didnt have a compression washer on it. Would also answer to the misfire...
Plugs went in before the cam change was even thought of, and i didnt do much mileage on them before a tapping developed, plug working loose?
The mis-fire was still apparent on start up, but cleared with a quick blip of the throttle, lifter pumping up to take up the play in the worn cam?
So new cam solves the mis-fire...
But new plugs cause another one along with a tapping noise.