Homesick, he's a grown man.
Not being near family / friends, getting constant grief from the missus (especially when he could be getting vast amounts of ££ more), not wanting his kid growing up in London, just not wanting to live in London himself... There's plenty of possible "homesick" reasons that he might want to move back up there and earn even more fortunes.
For him, why put up with niggles in his life when he doesn't need to. Most of us do it because we at least feel like we have no choice. He has a choice. Unfortunately for us.
I'm not saying I want him to go, I personally can't see how we'd replace him. But I can understand that there would be reasoning behind the move for him. Just not for us.