Cha cha is the least exciting of any dance, I think. The only ones I can remember from other series are Alesha + Matt's, and Mark and Iveta's.
To me, the steps are just 'mince forward, mince back, mince in a semi-circle, frot partner. Repeat ad nauseam. Look smug, particularly at the end.' Bleh. Not many places you can go with that.