Ok, some news. I have the head and block off. The metal is from the timing side little-end bush. The bush has been spinning in the con-rod.
I can also see that the camshaft and followers are buggered. I have a new camshaft that I bought from Andrew Guttman a while ago because the cam I put in the engine when I restored it was an old one that had been reprofiled, so I was expecting trouble. I've just been too busy, (or lazy) to strip the engine to change it!
So far, I know I need a timing side con-rod and cam followers.
The wear on the cam and followers explains the rather rattly engine when it was hot!