At last!!! It's fixed!!! I hope, I won't get too excited until she's had a few days under her belt.
So today I replaced the camshaft and fuel pump rod, put it all together, checked it was pumping fuel and went for a drive. It started better and ran better though the idle was still a bit wobbly, I got home and set about tunng the carb and that seemed to cure the hunting revs.
Finger's crossed team but I think she's fixed!! Thanks for all you help, advice and support along the way.
I'm a bit concerned the new cam will wear in the same way, there was no indication the first one was failing. That said, the replacement pump rod seemed nice and free moving, i'm using a different fuel pump, and there was lots of oil around the fuel cam, so it
should be ok.
As for the old camshaft, and spare engine, I was going to just use an electric pump if I ever needed it, but judging by what you say about Jim's experience Alan, I might try to fix the old camshaft. I have a mate who's Dad has a good lathe, I'll see if he can machine a it down. The off-centre circle will be smaller but I could compensate with a thinner spacer gasket on the fuel pump.
Thanks for your help once more everyone, epic problem thread signing out!