Update.
Well, I have replaced the Magnito coil. (Thanks to Neil Jarret) After a bit of mucking about I got it to start on Saturday.
Once running, it performed perfectly. No misfires. A nice steady beat. Tick over was slow enough for the clutch to disengage. Acceleration was smooth with no flat spots.
I took it for a short run round the yard before parking it up.
Today I started it again. Still a bit fiddly, but a lot better than before.
I am tracking down a Two Stroke post hole drill and I am going to see if it can be adapted to use as a starter.
I will keep you all informed.