Is there a way to change the crop labels that appear in C1. At the minute, mine are showing pixel dimensions but it would be useful to see them as, say, inches?
You set the units in the crop panel (see attachment).
Also, do I have to commit the crop in the same way I do in Lightroom (by pressing the "Done" button)?
No need to do anything else. Just select another tool than the Crop tool, e.g. the select tool or hand tool.