Rochelle Humes has a crush on Simon Cowell.

The Saturdays star - who has four-month-old daughter Alaia-Mai with JLS singer Marvin Humes - joked she would swap her handsome husband for 'X Factor' Simon Cowell because she loves his ''square hair''.

She laughed: ''The square hair cut just does it for me!''

Meanwhile, Vanessa White is a fan of returning 'X Factor' judge Sharon Osbourne, while Una Healy loves Louis Walsh because of his Irish blood.

The British band spent part of last year in the US filming their reality show 'Chasing The Saturdays' and have never been so nervous as when they met their favourite pop idol, Jennifer Lopez.

Rochelle said: ''I couldn't stop staring at her bum!''

The girls popped down to the Phones 4u flagship store on London's Oxford Street to celebrate Phones 4u's current social network #projectupgrade campaign, which aims to make ordinary people's dreams a reality.

The girls couldn't agree on what they'd like to upgrade about their lives given the chance, but the fashion-forward band admitted it would definitely involve clothes.

Rochelle said: ''I'd upgrade my wardrobe as half of it is maternity wear!''

Una quipped: ''I'd upgrade my wardrobe to Rochelle's wardrobe!''

The Saturdays' Una Healy, Rochelle Humes and Vanessa White upgraded Friday and unveiled the new iPhone 5S and iPhone 5C at Phones 4u, Oxford Street.