Progress update - I've been distracted by a couple of things along the way, so took longer than expected, but the engine is pretty much assembled. I picked up some engineers blue, finished the shimming, and it felt and looked pretty good. The cam holding tool from George came in very handy to nip up that retaining nut.
I lined all the timing marks up, then temporarily assembled everything in order to check piston/valve and piston/plug clearance, and after a few turns of the engine, everything still looks good with no evidence of clearance problems, cleaned everything down and reassembled.
Really the only thing left is to reset the ignition timing, and connect the coil and fuel - one for Saturday perhaps.
George, thank you again, once I've had a good startup, I'll pop your tool back in the post.
)