I Just came across this site – WOW!
UrbanGiraffe » WordPress Themes
Guides to creating your own themes
If you want to try customizing your own theme, then have a look at my WordPress Theme Dissection – a set of guides dissecting a WordPress theme and hopefully demonstrating how to begin customizing your own.
What can I say ?
This is a step by step dissection – with screen shots – on how themes work and advice on customisation. It is also available in PDF format as well.
Exactly what I have been looking for I must admit.
Obviously a lot of work has gone into this and the results speak for themselves – HAVE A LOOK!