Ant, if I could give you any tips it would be to watch your Histogram, and experiment more with your curves adjustment. If your using Photoshop, goto DeviantArt and download some photoshop actions, and then mess around with those.
The only way you learn is through trial and error.
Mess with blending modes, filters, etc.
The compositions are good, they're just lacking that Pazaz, that makes it pop. 👍