Niall Horan has joked he's glad One Direction haven't "gone Hollywood" since they starting shooting for their upcoming movie.

The British heartthrobs - also comprising Harry Styles, Zayn Malik, Louis Tomlinson and Liam Payne - are gearing up for the release of their hotly-anticipated documentary film 1D in 3D.

Niall is glad none of the singers' egos have expanded since their turn in front of the camera.

"We're still shooting at the moment. We forget the camera are there and just go off on a tangent. We're lucky enough that no-one has gone Hollywood!" he laughed in an interview with BBC Radio 1.

One Direction are busy with rehearsals for their upcoming tour in support of their latest album, Take Me Home. The extensive string of dates kick off in the UK later this month with the first show taking place on February 23 at London's O2 Arena.

Niall says although the five-piece are working hard to get their performances perfect, the band lose focus at times.

"We stopped doing dead arms when we were 12. There's an awful lot of messing around and making up stupid dance moves," he quipped.

"When we get hungry about 6 o'clock we get bored. We ran off the stage and told them we'd had enough yesterday."

The radio station premiered One Direction's new single for British charity Comic Relief this morning, a cover of Blondie's One Way or Another.

The band visited locals in Ghana earlier this year to see how the charity can help those in need, and Niall admits the trip had a profound effect.

"It was unbelievable, we had an amazing time. Even before we'd left on the plane to come back to London we asked them could we go back," he explained.

"It was a life changing experience. I don't think people believe how poor these people are until they see it. It was tough to see."