Spit,

If you're scratch building this plane, you'll have plenty of time to learn to fly while you build it. I scratch built my second plane, and by the time I had it done, I had flown 4 other planes and was ready for it. Building a ready made kit for a trainer or second plane might not be a bad idea for you, as you will learn many building techniques and answer many of the questions you have for yourself. Also, you'll have a trainer plane to fly so you can learn to fly that Spitfire when you're ready.