Its because the general view is better for taxiing, turning etc as there isnt so much wing/ struts in the way. When you land you stick your head out the side so it doesnt matter too much.
Its also to do with balance and on a Tiger Moth you can only see the fuel level if you're in the rear seat.
Ive done all my flying in the back seat, ive never been in the front which is sensible as that is where ill sit if I fly on my own.
Five hours on a Tiger Moth and straight onto a spitfire??? Dont be stupid that would never happen, they wouldnt even have soloed by then. They did about 50 hours or something on Tiger Moths , I think, then they went onto Harvards for advanced training and then went onto type. I dont think anyone should have been in combat with less than 150/200 hours or something. Ill have to look up that Dahl book, looks interesting.