Well, I’ve replaced the old brass plug with a new steel one and had it surfaced- a lovely repair, if I do say so myself, I just wish I’d done it the first time around.
I’ve dismantled the clutch, and it was pretty filthy with oil. Add one new clutch plate to the parts order.
There was a bit of burning on the pressure plate too- possibly it was working harder since the flywheel side was all slippery?
Keith Calver reckons my cam is probably salvageable, and has a put a set of his correctly reground followers in the post.
Everything else is ready to go, now it’s just a matter of being patient until all the new parts (followers, gaskets, clutch plate) arrive.