Thanks Beth. I'm currently carrying out further research on how a horse thinks (this one certainly has a mind of his own!) and I'm inclined to agree with your theory when I school him first. I guess the main point here for me is time, patience and determination.
I've owned my 9yr native cross for 8 months and he is very insecure when hacking out (alone and sometimes in company). When alone he will breathe heavy and go in reverse and with others, goes dead to the leg and sidels up to the other horse. These incidents happen 50% of the time. Sometimes...