Thanks for the feedback, it's all been useful. I've been working on it sporadically, ideally I need a few hours spare just for tweaking it.
skn3 - I've not adjusted the arms - I see what you mean, and from an animation point of view it makes sense to raise the shoulders and soften the joint area with loads of polys, but I prefer the lowered shoulders as it seems to suit the character more (I did try it out though - it just didn't seem right if that makes any sense).
ruz - The wireframe totals 3.5k polys at the moment - a bit too high really. I will try to reduce it down a bit before animating. Previously it was about 2k and I was happy with the shape, but I got carried away particularly with refining the glove hat and the hands.
Here's a latest shot, he's almost fully rigged now:

Hopefully after some poly reduction and tweaking I'll post some videos of him in action. :)