The Thetford c200CW is held in by 4 screws located in the locker base. Remove the cassette and look on the bottom of the locker for the 4 screws, 2 in each of the runners in squared off sections 2 at the front and 2 at the back that are hard to see. Remove these and you will also need to remove the filler tube housing, held in with 4 screws and is also sealed with mastic to the body so care is needed when prising it away because the plastic housing may be a bit brittle. Lift the toilet clear of the back wall and take it out. On some models the tanks are held to the back wall by means of a bracket that the tank is slotted on to, so lifting the toilet straight up will lift it clear just in case yours is one of that type. That's it, I thought it was going to be a hard job, it isn't, 8 screws and its out.
Hippytitimus, April 2013