The Orange was ClockworkGaz's - it is stunning, and a lot of work from a dedicated father.
Building from scratch was easy, buying second hand 24" wheels is the biggest minefield, I had more than one I had to return and in the end got it build up by Big Eck in macretro.
Cranks are also a hard find if you want style or retro, in the end I just got standard kids cranks from my local shop - they ordered them in.
The rest of the bike is a breeze you just buy sale parts or second hand, alivio stuff is so much better than the standard kids fair and isn't that expensive - pennies second hand as not many aspire to it.