Help!

I've got UK 1996 E38. My air-con controls are manual (four dials - left heat, air flow control, fan speed, right heat) plus three buttons to the left of the dials (air con on, air circulation, rear window demister).

Suddenly today all the air con functions have stopped working - I can't change the air direction or temperature, and the air con, recirc air and demister buttons aren't working either. I can however turn the blower on and off and adjust it's speed. In addition I've noticed a ticking from the engine compartment, at the rear by the bulkhead. This happens every three seconds or so, even when the engine is switched off / no key in the ignition. My guess is that a stepper motor ahs got stuck and has blown a fuse or something. Anyone have any ideas? Whilst I'm on it, I've never been able to get warm air out of the vent in the rear of the front armrest (for rear passengers) - only cool air. Can anyone help??