Triton Rapide 4 shower?

Shower about 2 years old and has always worked well. During use yesterday there was a smallish clunk from the shower unit. On investigation there is HOT water leaking from the bottom left of the unit and COLD water coming from the shower head. Please advise if you think this is repairable and could be done by myself, and approximate cost. Many thanks.

Desperatetoshower
November 2010