Hi mate, well firstly let's hope that Robin is O.K.
TCL??? You sure about that?
? I have no reference to TCL as a fault code, not in my copy of he instruction anyway.
However I would put my money on it being the thermocouple.
Take out the thermocouple wires from the back of the controller and replace them with a link so that it short circuits the connections.
Turn on the controller and it should read room temperarture, 18 degrees or whatever.
If it does, the thermocouple does indeed have a problem. If it still reads the error code then the problem may well be in the controller.
As for the damage in the side wall...complete red hearing as you suspected, however, do make sure the element is not now visible, it won't effect how the kiln works if the elements is visible but it will make your hair stand on end if you touch it when the kiln is on