Yep - decided to move the mean male, and a couple of females to a separate tank. He's not roaming the tank much, but when I come in and sit opposite, he'll come over to me whilst I'm there. Then return to his corner when he's bored of me.
Just tried a ping pong ball to entertain him. He found it very interesting, and went up and touched at it - so I think thats enough progress on the entertainment side of things for today