Harry,
I did as instructed and ran Auto levels followed by the action available for download in the Processing False Colours in this link and it came out like your final result. Quick and easy.
http://khromagery.com.au/digital_ir.html
I tried this proceedure the day before yesterday on mine and all I got B&W, so it is definately down to your method of setting custom white balance.
I'll have to take a trip into the loft now for the D100 manual.
Don