Black Ink really is a genius idea!
I wish I'd thought of it...
After reading the first reply I decided Codex Grey must simply be too light... I mixed it with Chaos black and dry-brushed it very carefully... it's come out alright but unfortunately I am using a Cadian officer's body so there isn't exactly too much higlighting to do, the model is a bit boring to look at...
Maybe I'll tinker with it later but at least it's looking ACCEPTABLE now, thanks a lot for your help guys