Whitbread - who recently appeared on I'm a Celebrity - will team up with comedy group The Cuban Brothers for the spoof dance contest, while Drew-Honey is paired with Tracey Beaker actress Dani Harmer.
Former England cricketer Darren Gough - who won the third series of Strictly Come Dancing in 2005 - and comedian Miles Jupp will take on solo routines.
Olly Murs, Ulrika Jonsson, Scott Mills, Omid Djalili and ex-The Only Way Is Essex cast members Amy Childs and Harry Derbidge have previously been confirmed to appear.
Graham Norton, Keith Lemon and Inbetweeners star Greg Davies have been confirmed to judge the first week.
Alex Jones and former X Factor USA presenter Steve Jones will reunite as hosts of the BBC charity fundraiser.
Let's Dance For Sport Relief runs on BBC One for five weeks starting Saturday, February 18.