Thank you Jim. The right advice as always.

Erics - What Stefanos illustration doesn't show is that the 3-way in the Semi is hard wired. It doesn't have a plug on the coil but two wires that exit the coil and go down the chrome tube into the base where they have crimped bayonet connectors that are too big to pull through the tube.

Thus you either have to cut the wires in the base and join them up again or cut them under the bell and put connectors on. Changing the solenoid is a piece of cake. The coil is a roast dinner - well, almost for somebody as ham fisted as me..

I don't know if a plug conversion will fit under the bell but I doubt it. Maybe someone has done it.

I'll strip it down and descale in the next day or so. Learned opinion is a new 3-way will not be necessary. I have been a bit remiss lately because the water is soft to start with and goes through three filtration systems.

You might just be able to clean the pilot and might as well the gigluer without needing to actually replace it (the solenoid),
I see the valve getting stock often on semi-auto,
sometimes a little tap (after removing the fancy cover) with the back of a screwdriver gets the valve unstuck sometimes not
most likely your coil is fine but if not
the wires need to be feed in the pipe and the terminals crimp on.