"I think she (Williams) was probably getting a bit edgy in Australia, just being the two of us," McFadden said.
Since the move, McFadden has released a new album and has started touring again after supporting his mentor Ronan Keating this year.
"It was my first time touring in eight years and I didn't know how it was going to be," he said.
"When I got such a good response after the first few gigs, I thought if ever I was going to come back and put an album out and do a tour, this was obviously the time."
Williams, 27, said they would like to start a family.
McFadden has two daughters Molly, 11, and Lilly, 10, from his first marriage.
"I don't feel I'm in any rush, but it's one of the reasons I wanted to make a base here," he said.
"I think 30 would be a good age - I still have lots of things I want to achieve."
"I'd like to see Vogue concentrate on her career. I'd be happy to be a stay-at-home dad."
- PAA