The 22-year-old singer, who quit the band six months ago in order to live a "normal life", is currently Stateside working on solo material and does not look set to move back to the UK anytime soon, reported Aceshowbiz.
"He definitely seems happier over there and doesn't act as though he wants to come back to the UK any time soon.
"It's the lazy Californian lifestyle he loves. What he said at the party sums up his attitude. He's done with Britain," a source said.