I would suggest putting some Vanish powder (for washing machines) in the saucepan, adding some water and then heating it on the cooker. When it comes up to the boil, switch off and leave it overnight. Then empty the water away and scrape away all the burnt stuff you can.

You may have to repeat this, depending how badly burnt the saucepan is. You will have to use some elbow grease, but it will be worth it if you save the saucepan.