Thanks a lot for taking the time to help, I've taken it all on board and will look to improve the areas I can, and certainly keep the advice in mind for the next creation.
In answer to your points;
1) I definitely need to work on my anatomy in general, and will look to make improvements either on this one or the next iteration.
2) I've struggled a bit with rendering as most pieces I've experimented with in the past end up looking "soft" and airbrushed, just all in all "too digital" if that makes sense? So I added a bit of texture to try and avoid that. Maybe I will remove this from the armour pieces and keep it only on the cloth areas.
3) for perspectiive I used a digital manikin on an ipad app I have as reference which comes with some good perspective features, and I actually thought I'd got it pretty spot on with some very minor flaws. I think the neck area is suffering perhaps due to the dramatic angle in which he is positioned, coupled with the ambitious contours of the of the neck armour. I will look to make some adjustments though.
4) I think trying a large rocket launcher type weapon could work really well, awesome idea there thanks! I'm also toying with the idea of making the rear of the orange armour area on the torso a jet pack - I'll see how it works out when I start sketching it out.
Again, thanks so much for your advice. Like I said, this is my first piece really that hasn't stemmed from a tutorial so I'm very much a beginner looking to improve in every way I can. I am really happy with the start I've made though, once I get more practice in I think I can start producing some better quality work