London Community Gospel Choir are also a new addition to the bill.
Blue, JLS, Lemar, Sugababes, Right Said Fred, The Automatic and Liz McClarnon have previously been confirmed for the event, which takes place on August 8.
Former X Factor stars Chico, Andy Abraham, Eoghan Quigg, Rachel Hylton, Austin Drage and Laura White will also perform.
The festival has been organised to support premature baby charity Just 1 Life and will raise funds for neo-natal units across the country. Tickets are still available.