The Hoosiers and Welsh rockers Kids In Glass Houses have also been announced to play the one-day festival, which is held in Weston-super-Mare.
They join a long list of confirmed acts, including JLS, Pixie Lott, Dizzee Rascal, Alexandra Burke and Tinie Tempah.
T4 presenter Miquita Oliver said: "We're almost there and 4th July can't come soon enough! It's always my favourite day of the summer and I'm looking forward to seeing what all of the acts have up their sleeves when they come out on stage."
Tickets have now sold out, but the event will be broadcast on Channel 4 from 2pm.