Hi Neil, by coincidence I have just had a heater failure on my Creda tumble dryer. I too noticed carbon deposits near the rear bearing but felt this was incidental & suggesting a dry bearing so I lubricated that and sqeaking stopped. The heating elements on mine looked intact & there was no evidence of overheating, scorching, etc. So I checked the 2 thermal cutouts above the heating elements using a multimeter (obviously with the dryer unplugged!) to find (after diconnecting the power spades) one of the sensors allowed no current through.
This I have now sucessfully replaced. You should check for a cause of the overheat or it may just cut out again. Air intakes or vent pipes may be clogged.
I may be telling you what you already know, but if not I hope this is helpful.
charlie b
charlie buck
August 2007