OK called in Damus the supersweep / mechanic and he said its operator error:
ie. I made an error in thinking I am a bike mechanic.
He said he has no idea what I was measuring but the intake valve clearance is bugger all and needs re shimming. He also suggested that the new spark plug i put in must have been second hand. Although on closer examination the new one was actually in the spares box, so not sure what i was doing that day. perhaps I should stick to my day job.
So to avoid me cocking it up any further when I get the new shims he is going to supervise me putting it back together as apparently he doesnt trust me – no idea why.