I have installed the NOOBS files per instructions. When I start up, I get stuck on the coloured screen. The troubleshooting guide indicates this is due to missing/corrupt kernel.img. Where should I get this file from - it is not part of the NOOBS download (unless I'm missing something stupid).
It is part of the NOOBS download - assuming you're using Raspbian or one of the other OSs in the NOOBS package. The installation process will place it in /boot/kernel.img.
I would try the installation again, either on a fresh SD card or reformat the one that failed. It sounds as though it simply corrupted in some way.
Check that the card is large enough to hold it - minimum of 4Gb and I wouldn't use anything slower than a class 4.