>My partner has become increasingly bad tempered and shouts at me quite a lot. He usually denies that he is shouting. He does a lot of childish blaming, i.e. it's never his fault. It has become increasingly hard to bear. He has another side to him which is kind and conciliatory, but I'm seeing it now as co-dependent behaviour, rather than genuine loving and caring, i.e. his kindness comes with a contract. He has been attending a codependents' group for a year and I have noticed some small changes, but the fighting has continued and even escalated.
>Most of his outbursts are triggered by problems with his family, (he also has many arguments with them) which he acknowledges, but I seem to have become the target of his frustrations.

This sounds like a typical rut where you would have to keep calling the person on their ***** until they finally get it. Set limits. Assert yourself. I've been through something similar. Once he takes responsibility and really starts letting go of the neurosis (codependency) things will improve. Until then, it's resist or give in, both of which are draining.