Andy, I've tried many ways to achieve what I want, but have always found PS wanting in this area.
I used to do quite a lot of IR back in 2002 using my Minolta D7 + the hoya IR 72 filter.
Here is a couple of photos from that period, that will give you an idea of what I want to do.
http://i79.photobucket.com/albums/j1...RapeFields.jpg
http://i79.photobucket.com/albums/j1...on/IRImage.jpg
Harry