Busted piston rings.
Air seeping past intake manifold gasket leading to lean running.
Burned out wiper motor.
Rear brake drum warped - needed replacing.
This was a lot of fun - but not very practical.
Apart from the breakdowns, we lived in Wellington and had no garage - so: lots of rain got into the car. My wife's caged bird that she took to and from school (teacher) used to kick seed out of his cage - it fell on the wet carpets and sprouted.
Now, as for the breakdowns... we bought this car as a restored classic from some asshole who had made a really shoddy job of it. He'd cut corners and pinched pennies and basically relied on a decent paint job to sell the car. The gearbox was from a Herald. It worked OK, but the gear lever travel was wrong and it banged into the radio knobs. The brakes were not right and needed several trips to a specialist to sort out, the wiper motor died, the motor just wouldn't run right until after I'd given it a valve grind and replaced just about every gasket on the intake side, plus replaced the SU needles and fiddled around endlessly. The seats turned out not to be black leather, but red with some kind of nasty dye on them that peeled off and stuck to our clothes.
Moral of the story: if you buy a restored car be very very careful about what you are getting. We really enjoyed the Spitfire for the short moments when it ran right. We sold it after only about nine months as it was too hard to keep it running.
Spitfires are cheap cars that generally received no support through their life. I owned a 72 and suffered through 2 years of problem solving. The good news is that once I sorted the car out (correcting the previous owner's poor work), I enjoyed my MK4 Spit without problems for 9 years. Sorry your experience was so negative. Spitfires are a blast. If properly set up and maintained, they are cheap to run.