He does respond well to training. When we're home he usually wants to be around us, but every now and then he will take himself outside. Once he gets into fence pacing mode it's hard to get his attention. If I've got food he is easy to persuade though and he will do ANYTHING for food.
In that case I would build him a run, preferably square, not long so he can be in there when you aren't home and has nowhere to pace. He may grow out of it as an adult if he settles down a bit. Let him have the run of the yard when you are home and use something to distract him if he is fence pacing, like throwing a chain against the fence, then calling him and rewarding him if he comes. He will catch on to the sound of chain and come when he hears it. I had one like this and it got to a point where I only needed to clink one link of the chain and she would come from anywhere.
Thanks for the advice! This morning I set up a bit of a makeshift run so i'll see how that goes. Not sure how big to make it but it was about 5mx4m with access to the outdoor laundry. I'll make sure I'm outside with him and distract him when he starts pacing.
I am really hoping he does settle down a bit when he matures a bit more.