Rachel, not really an answer but i have exactly the same problem. With mine the "drying" light does not illuminate but sometimes flickers as i turn the timer knob and there is a slight electrical smell. I have seen on another website that it is a fairly common problem for the heating switch inside the timer unit to burn out and therefore everything works but the heater itself is not turned on by the timer unit. I am currently looking for a timer unit cheaper than £47.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix tumble dryers.