You won't have any voltage at king lead unless engine turned over and this will be thousands of volts which your voltmeter woulden't be able to read, I think the plug on side of dizzy you talk about is for the electronic module (Effectively an electronic switch for coil)

You should have +12V to coil one side and the other is switched by above method it's actually when the earth is broken you have power at king lead due to voltage collapse inside coil.

Depending where in Dartford you are I may be able to help you?

Martin