Answer by taking a quote from the following article:

Xenomania is an English songwriting and production team founded by Brian Higgins and based in Kent, England. Formed after Higgins met Miranda Cooper, Xenomania has written and produced for renowned artists such as Cher, Kylie Minogue, Dannii Minogue, Sophie Ellis-Bextor, Pet Shop Boys, The Saturdays and the Sugababes. In particular, all but one of Girls Aloud's studio albums have been entirely written and produced by Xenomania. Sugababes' "Round Round" and Girls Aloud's "Sound of the Underground" have been credited with reshaping British pop music for the 2000s.

Xenomania worked with American pop singer Britney Spears in 2003 during sessions for her fourth album In the Zone. The song submitted, "Graffiti My Soul", was not chosen for the album. While the record company loved the song, Spears felt that it needed more of a chorus. Higgins said that they wanted "essentially 'Sound of the Underground 2'." It later appeared on Girls Aloud's What Will the Neighbours Say?.  The production team were due to work with rock bands New Order and Franz Ferdinand, but both sessions proved fruitless. Xenomania was due to produce for New Order's Waiting for the Sirens' Call, but Peter Hook said they "scrapped the Brian Higgins stuff because we didn't like it. I thought he did quite a good job on Girls Aloud but he didn't do a good job on us." Franz Ferdinand's drummer Paul Thomson said, "We wrote with Higgins for a while and initially we thought we'd work more with him but it didn't really work out. We just realized that we're not really a pop group."  Xenomania were reported to have written five songs for Leona Lewis's second album, Echo (2009), described by Cooper as "tragic songs with a twist". The songs did not make the album. In 2012, Xenomania were reported to be working with Christina Aguilera.  Higgins spoke of bad experiences with bigger artists to Literally magazine in 2009:  "Everything about us is about enormous enthusiasm for something. And therefore big artists can come in and they think "they're the flavour of the whatever, let's take their thing and then we'll do what we want with it..." Well, no, that's not acceptable anyway. I've had that experience happen where the big artists were fine until they got into the mix room and then they basically pulled the record to pieces. So I took my name off the record and the writing credits off the record. Because they're assholes. And they sold about 20,000 copies, and they've never been seen since. So big artists are often jerks of the biggest order. And often people say don't meet your heroes because you'll be let down, and I sort of understand why people would say that."

Is there anything else they said about working with Xenomania ?
Higgins spoke of bad experiences with bigger artists to Literally magazine in 2009: