Many thanks for all the replies on this one, I appreciate all the tips, sorry for the slow reply, had to pack up some orders to go out.
I just lifted up the bonnet on the Gottlieb, located the EOS switch, gave it a light file with an automotive points file then cleaned with some metho. Checked the coil for open circuit, wasn't sure which was the primary winding and secondary winding but got continuity through all 3 points so guessing the windings are intact.
Started up the machine but still got the crazy flipper action. Not sure where to go from here, maybe time for a new coil???