Symon, I've looked, and all lobes seem fine.
I found 2 tappets that have slight play in them. I can push them down slightly by a mm or two, but only 2 of them, all the others are firm and can't be pushed/moved by hand. 1 is on the inlet cam, and the other on the exhaust cam.
Does this sound like what will be causing the noise?
So, next question, if these tappets are the culprit, what's the proceedure to replace them? Can I just remove the cam shafts to get to them, or is it a head off jobby?