@ DJ Ah, I didn't know there was a select on click option in PS! Must look into that! Thanks!

@Rev: I finish all the artwork without the labelling in Photoshop and then bring that into a vector program to label it, so the artwork is on layer 1 and the labels are on layer 2. If I need to tweak the artwork, I just replace the underlying picture. I do most of my mapmaking in Serif Drawplus, which is a Vector / Raster Hybrid, so I can do pretty much all of this in the one application, but sometimes Drawplus doesn't get exactly what I need, so I'll use PS.