Did you get helped last year? If so please ignore. Otherwise....
Hi. You can locate a Sunbeam Service Centre via http://www.sunbeam.com.au/Pages/Support/Repairers.aspx
You're looking at $69,95 recommended retail.
BTW have you checked that it's not the blanket? Swap the controls over, if the problem follows the control it's the control. If the problem stays on the same side of the blanket, it's the blanket.
Also note Sunbeam has a 3 year warranty on electric blankets. If Date Of Purchase is less than 3 years ago call 1800025059 option 1 to speak to their Customer Service,