... there are some tricky connections concerning the power wires, grounds and isolating washers etc. I spent HOURS on this problem on my son's MGB years ago
That is indeed true for the Lucas DM2 and 25D distributors. The proper placement of the insulating washers is imperative. However, this Spitfire has a Delco dizzy so it won't have this particular problem.
I'm glad you got spark now. However, you are not really done with the ignition just yet. You said this is a 1.7 Ohm (ballast) coil. That MUST be supplied normal running current through a ballast resistor (or resistor wire). Failure to include the resistor will result in premature failure of the points and other ignition components. Don't worry about it for just getting the engine started but do address the ballast issue before you start driving the car regularly.
If this car sat for a long time you can anticipate needing to clean the carburetor jet tube, metering needle, and float valve. They tend to gum up with old fuel. Also, if this is the original Stromberg carb you really should fit a new diaphragm as sitting for a long time can cause those to harden. Hard diaphragms won't allow the piston to rise and fall properly creating all sorts of running/driving problems.