Ros,
Something I forgot to mention when using Control Points on an image you intend to crop.
1) Either crop first, then process - or
2) Process then save as an edited version. Re-open the edited version then crop.
This is because Control Points and Black, White and Neutral points reference from the top left corner of the image. So any crop that does not include that will cause the points to be displaced.
See post #77 and #78 on page 8 for an explanation that includes screen grabs to see what happens to the points when you do crop with them active.
Have fun
Don