I've been exposed to similar situations as this Graham. If the company feels it's in their (or mutual) best interests to end the relationship they may be willing to provide a written positive reference to expedite that. It's worth asking - 'hey guys, this clearly isn't working out and it's not in our best interests to keep trying, I'm happy to start looking for other opportunities if you're willing to help with a good reference for me' - and, depending on how much you can tolerate, you could even negotiate to stay on whilst you're looking for a new job, perhaps in a reduced capacity if required or desired.
Best wishes mate, these situations are sh*t.