I left this thread last night as I was too emotional, but wanted to return to answer some questions and clear some things up. Sorry if I don't answer each individual post, all these replys are rather overwhelming!
Val is helping me rehome my dog to a good ethical rescue hopefully and is taking a lot fo her own time to help me with this which I truely appreciate. Val has not lead me in any way, we had already spoken over pm about my dog previous to this incident and she did not ask me any leading questions or sway me in any way. 
As for the whole arguement about was it a bite, a nip, a snap, etc. I don't fecking care what you want to call it really! I used the word bite in my op. It was not an aggressive move he didn't growl or snarl or lunge at ds, however he did use his teeth to hurt him and he left a mark. Call it what you want it doesn't change my current situation.
My dog is a collie cross. He is affectionate, bright, good company, gets on with other dogs etc.
I don't completely blame the pound, I accept the fact that he shouldn't have been placed with me and I shouldn't have homed him. I had a collie cross growing up and this coupled with how reassuring the pound where that he'd be fine - and the fact he was in a cold wet icy kennel meant I took him home with me. I visited him there almost everyday for two weeks, and had a trial weekend that he never returned to the kennel afterwards.
I will not be keeping my dog 
I do not want him put to sleep
DS is comfortable with the dog on a lead and he knows he will be going somewhere else as soon as I have found him a nice place. This is a short term situation from my point of view and DS knows that.