The charity event is to be held at London's Wembley Arena on October 10.

Joining them at the gig will be another Pop Idol contestant Zoe Birkett.

The trio will join music's big earners after announcing the 14-date tour called Will Gareth.

They are also set to make a fortune from merchandise and record sales on top of earnings from tickets, reports the Sun.

Will and Gareth are signed to Simon Cowell's BMG label and Zoe is expected to follow soon.

The full dates are as follows:

It will start in October with 16-year-old fellow Pop Idol finalist Zoe Birkett in support.

The tour will kick off with two dates at London Arena on October 3 and 4.

She told Ananova she's had no time to see him or Will Young because she's promoting the Pop Idol album.

Zoe and Gareth have denied they are going out even though they admit they are close.

She said: "I did a radio interview with Gareth yesterday but we're both so busy we only really had chance to say hello.

"But I speak to him on the phone nearly every day and send him loads of text messages.

"Will's taking a break at the moment so I haven't really had chance to catch up with him."

Zoe says she is to concentrate on the big band sound following the recent Pop Idol tour.

She says singing with a live orchestra is what she does best.

And she is looking to release her version of Judy Garland's Get Happy hit as a single.

The track is featured on Pop Idol The Big Band Album, which was released on Monday.

Zoe adds that she's flattered by all the attention she's been getting from fans.

"Being in the spotlight is brilliant. I'm really flattered that so many people recognise me in the street but I don't feel any different. I'd say I've learnt a lot more about myself and matured. I'm now much more confident as a performer," she said.

"I've been surprised by the long hours I've had to work. But there's been no big shocks about the pop industry yet. I'm still waiting."

She is considering releasing her cover version of Get Happy.

The track appears on Pop Idol The Big Band Album, which is released on April 8.

Garland originally sang Get Happy in her 1950 film Summer Stock.

Pop Idol The Big Band Album features all 10 finalists singing their favourite swing tracks from the series.

It will be released on April 8.

The singer had to miss last night's performance at the London Docklands Arena because of tonsilitis.

But she is expected to re-join the nine other finalists at Sheffield Arena on Thursday.

A spokeswoman told Ananova: "Zoe was devastated that she had to pull out last night but she is concentrating on getting better for the Sheffield gig. Doctors say she should recover in time."

The show features Zoe singing a piano duet with Pop Idol runner-up Gareth Gates.

He will be joined by runner-up Gareth Gates and the other eight finalists for the first date of the Pop Idol Tour at London's Wembley Arena.

Fans snapped up 18,000 tickets for the first two Wembley gigs in just two-and-a-half hours.

It will be Will's first public performance since he revealed he was gay but the revelation has failed to dent his appeal to the record-buying public.

His single Evergreen/Anything Is Possible looks set to hold on to the number one spot for a third week and has shifted 1.5 million copies so far.

Gareth, who releases his debut single Unchained Melody on Monday, will perform a duet with fellow finalist Zoe Birkett.

There were rumours of romance between them after Gareth broke down in tears when Zoe was voted off the show, but the pair have insist they are just good friends.

Other familiar faces performing on the tour will be Jessica Garlick, Rosie Ribbons and Darius Danesh.

The 21-date tour will visit Sheffield, Birmingham, Manchester, Glasgow and Newcastle before ending with a special Royal Command performance.

The Pop Idols will perform in front of the Prince of Wales at a concert in aid of The Prince's Trust on April 6.

Chloe Hazlewood and Faye Cowig, both 15, of Witham, Essex, have been kept at home after teachers objected.

They had the £85 extensions woven into their hair in the style of Pop Idol finalist Zoe.

John Bramston School believes "attention-seeking" hairstyles are not appropriate and decided the pair should be taught away from other pupils, but they have not been excluded.

Headteacher Ted Rowley said: "This is a school with very high educational standards and very high standards of dress. In relation to hair the school rules state hair should be neat and tidy and that extreme or attention-seeking styles are not appropriate."

Faye's mother Janie Cowig, 39, said: "At the end of the day how does a hairstyle affect using pen and paper? I'm adamant, we are going to stick to our guns. I know the only one I'm harming is Faye, but she doesn't feel it's fair."

Chloe Hazlewood and Faye Cowig, both 15 and of Witham, Essex, have been at home for more than two weeks after having waist-length blonde extensions woven into their hair in the style of contestant Zoe on the ITV show Pop Idols.

Their parents decided to keep the girls at home after staff at the John Bramston School in Witham said the pair should be taught away from other pupils for fear of causing a distraction.

"As far as I'm aware the girls have not broken any rule and I can't see the problem. Their hair looks nice," said Faye's mother, Janie Cowig, 39.

"I'm waiting to hear from the school to see what happens next. This is the third week they've been off and I've heard nothing."

Mrs Cowig said she was concerned because both girls are due to take GCSE examinations later this year.

Staff at the school were tonight unavailable for comment although it is understood that the school has a rule which says that attention-seeking or extreme hairstyles are considered to be inappropriate.

Fellow reject Hayley Evetts has also decided to stay in London to support the remaining trio of Gareth Gates, Darius Danesh and William Young.

Pop Idol returns this Saturday at 6.10pm.

Evetts said: "I've been in the flat ever since I was voted off. It's weird being there when you're not taking part in the show, but I've enjoyed myself.

I'm not ready to go home yet and I want to be around for Zoe because I know exactly how she feels.

Hayley watched the show on Saturday, but refused to sit in the studio audience.

"It would have been too painful. I don't think I could have stopped myself from shouting out when the judges made nasty comments and said they thought Zoe would go."

And the 16-year-old says she is not going out with fellow contestant Gareth Gates.

Zoe says Gareth is more like a brother to her.

Zoe, a 16-year-old A-level student from Darlington, was voted out of the running after a record 3.6 million calls.

She said the defeat had upset both her and Gareth.

"As I've been with Gareth since the beginning of the competition at the Criterion auditions, I'd like to see him win," she said.

"He's a strong person, who has put up with a lot from people, and he's funny as well."

Should Gareth triumph in two weeks' time, she did not think his stammer would prove a problem in his bid for stardom. When he does become a star, I think he'll be fine. He'll be able to put time aside to practise and rehearse."

Zoe insisted she had learned a lot from the experience, and valued the judges' criticisms of her performance.

"It's the first big thing I've done. It's big advice for me, and next time I'll know what to do. Although it's criticism, it's constructive. This time last year I never would have expected to be doing this," she said.

The 16-year-old A-level student from Darlington broke down in tears and was hugged by fellow contestant Gareth Gates after being told the news.

She sung the Whitney Houston hit, I Wanna Dance With Somebody, and the Jennifer Rush ballad, The Power of Love, but did not win over the judges who all predicted she would be the next to leave.

Publicist Nicki Chapman told Zoe: "Last week I thought you did the best performance by far. This week I'm not convinced."

Record producer Pete Waterman said: "The songs were just a little bit above yourself."

This week's episode differed slightly from previous weeks with each contestant singing two songs each, with the theme being former number ones.

More than three million viewers voted for their favourite performer on the show.

Zoe finished behind 17-year-old Gareth, favourite to win the competition, student William Young, 22, originally from London and Darius Danesh, 21, who is studying English at Edinburgh University.

During the show Gareth denied reports in the press he and Zoe were dating.

But they say they have formed a close bond since taking part in Pop Idol.

The pair are said to text-message one another constantly, leave notes in each others dressing rooms, laugh at the same things and play fight.

Zoe is also helping Gareth over come his stutter. He holds her hand and looks into her eyes to help him focus when he's answering questions from the media.

But Gareth tells the Daily Express: "We're very close but we are not going out like girlfriend and boyfriend".

Zoe says Gareth has become her best friend and hopes they will be friends for life.

Its boss says he is making sure diners vote for her.

Sixteen-year-old Zoe, the youngest contestant on ITV1's show, is one of the favourites to be voted off tonight.

Antonio Alessandro, owner of La Famiglia in Darlington says she was like a member of the family.

He plans to pass his phone round to diners to make sure they register a vote for Zoe.

"All our regulars are backing her," said Mr Alessandro.

"I tell them to vote for her and when they get their phones out I say 'Don't worry, we'll do it for you from here.'

"Zoe is like one of the family and we all wish her the very best of luck.

"We think she'll get down to the last two at least and whatever happens on the show, she will be a star."

She dislocated her hip trying a "tricky dance move."

The then 13-year-old spent a further year on crutches.

Zoe, now 16, and the other remaining finalists have to perform Big Band songs on Saturday's show.

She said: "When I was just 13, I did a tricky dance move and dislocated my hip. It was agony and I was rushed to hospital."

She was forced to stay off school for months and take part in painful physiotherapy.

"It was during that time I discovered that I love singing. I can do some dancing now but I'll never be the same again."