Ok guys, got everything back together - however.
As I was taking the rocker covers off to check clearances, one of the small washers escaped and fell inside the engine. I could hear a tink, tink, tink and hoped it'd fallen outside, but apparently not. Its not in the rocker 'void' so I reckon its fallen down the push rod channel. Thought it might pop out onto the sump gauze so kicked it over a few times and checked - no washer. In the end I thought %^&$ this, I'm not taking the engine apart for a small, thin, mild steel washer, especially as this engine seems to chew up other things and stick them in the sump gauze. Fired the bike up (second kick), no knock from the engine (see previous posts), and it ran perfectly. Still no washer in sump gauze though.
So, what's the worst that can happen folks??