Ore Oduba and Sonali Shah (from Newsround, apparently) have also signed up.
ETA: A full-ish list from the Beeb site.
Ore & Sonali – Newsround
Rosemary Shrager & Kim Woodburn
Shaun Keaveny, Mark Dolan and Hal Cruttenden
Hmm why is Lee Nelson doing it again? he was rubbish last time.
are Shaun, Mark and Hal doing it as a group?