Follow on to earlier answer:
Check the question "Howto replace the belt on a Creda Simplicity 37761?" to get access to the jockey wheels
Dave
April 2009
Hi Steve
I have the same machine which had this fault, turned out to be one of the jockey wheels which the belt runs on, and cost £6 to buy from a repair shop. These are a weak point on these machines. Failing that I would guess the drum bearing. HTH