What can people expect from your appearance at the Bearded Theory festival?
"I spent three months with the X Factor tour, I came back from the tour and then I had a gig in Scotland, and from Scotland I went straight to Italy to do a TV show, and I came back yesterday from it and last night I had a gig here in England. I'm only going back home now. So I'm not sure yet if I'll be singing to backing tracks or with musicians, but what I will certainly do is sing fun songs and beautiful songs. And definitely what I like and what I'm given the chance of singing. At The X Factor, I never chose any of the songs. They were all given to me and I didn't know them, so I was at the last minute trying to learn the lyrics!"
Will you be singing any songs from The X Factor?
"I might, I might. But definitely there'll be something new."
Will you have the bongo drums and dancing women with you?
"Bongos are the small ones! They are congas. Everybody, and I mean everybody, calls them bongos but really their name is congas. I always play my congas in my gigs. Always."
Good! What about the dancers?
"I don't know if there are going to be any dancers. I need to talk to everybody to see if I will bring them. I don't know much about it because I was so busy with the shows. It was a very tight schedule and just like when we were at The X Factor, we were quite away from the real world - security, coach, hotel, fans at the hotel, and we couldn't go anywhere. There were many days we had two shows which wouldn't give us time to do anything else. And we had to give our best performances because the audiences were huge. At the O2 in London we had 22,000 people, so it's a big responsibility. You have to give your best. But now I will think about the Bearded Theory festival."
When can we expect a single and an album from you?
"I don't know yet. It's certainly something that I would like to have."
When you were on The X Factor some people said you aren't a serious musician. Did that upset you?
"Of course. The tabloids labelled me as an alien and never ever correctly called me British Brazilian, and always said that I could not sing and stuff like that. When I did my first audition I sang 'O Sole Mio', which is a classic, and the papers were comparing me to Pavarotti. And when I went to Boot Camp I sang Leona Lewis, 'Footprints in the Sand', and Nicole Scherzinger from the Pussycat Dolls cried with my performance. When I was brought back as a wild card I was given fun songs and songs that I've never sung before and never even paid attention to. With the schedule of the studios and the X Factor filming for everything, the website and the show itself, we were given very, very little time to learn the songs. I am a Portuguese speaker so it is much easier to sing a song well when you know the lyrics and then you know the song. But if you don't know the lyrics you can't even get the melody right because each syllable is a note and if you don't know the lyrics... I was given very fast speaking songs, and I had difficulties in learning them. But I did them! Backstage I was listening to my iPod and the lyrics, saying, 'Oh my gosh, I can't forget these lyrics'. I managed to do them but I didn't do them to the best of my ability because of the shortage of time."
The press also said other things, didn't they?
"They started to say I was illegally on benefits when [actually] I had had three operations on my shoulder. That's why sometimes I was holding the microphone with two hands because one arm only couldn't hold the microphone. And they also said that I had walked into Mary's bedroom and she was naked. Please! That was a lie. They said that I had booted Harry from One Direction. It was just one lie after the other. But I've learned not to bother. I've learned [to think], 'Right, never mind'. What can I do?"
There's been a lot of talk about who will be a judge on The X Factor this year - who do you think should be on the panel?
"Well, definitely Simon has to manage to come back here. He'll probably be a part-time judge. I don't know. He might not be able to be here every show, or he might. But I think definitely he should be. And I can't see anything wrong with any of the judges. I think Cheryl is so beautiful and she's a great performer. And Dannii is so lovely backstage. I saw her baby and what a gorgeous baby he is! Louis... the best definition for Louis is the one that Simon gives - Louis is mad!"
Are you still in touch with Louis?
"Sometimes I text him and he texts me, but not a lot because he's not my manager and he's so busy with his affairs and with his business."
Would you be a judge on The X Factor if they asked?
"It would be a very pleasant job to do, I think!"
Who do you think will be a big success from your series of The X Factor? Cher, Matt, Rebecca, One Direction... who will do the best?
"It's very difficult to say. Rebecca has an incredible voice. Cher is so interesting - so petite and so full of energy at the same time. Paige has a fabulous voice. My God, Paige's voice is amazing. Aiden is a gentleman. I don't know anyone more posh than Aiden. He's such a good friend. All the boys from One Direction are lovely boys, really good role models to all the British young men. And Matt is a great singer. The first time I heard Matt at Boot Camp I said, 'Oh my God'. So it's hard to say. Katie - she's very cute and I don't think she was given the best songs for her voice because I have heard stuff that she likes to sing and it sounds really amazing. And Mary, Mary definitely will have a career in Ireland and in the UK. I can't see why she couldn't go global. She has a very powerful voice and she's a great character. She's a great lady. Have I missed anyone?"
How do the public react to you when they see you in the street or when you play shows?
"I am blessed that people like me a lot."
There's a lot of love for you on Digital Spy - would you come and play a concert for Digital Spy fans?
"I like to sing anywhere at any time. Nothing gives me more pleasure. So I would be honoured by your invitation."
Wagner will be performing and have a meet-and-greet at the Bearded Theory Festival in Kedleston Park, Derbyshire on Sunday, May 15