Circuit protection fuse and MOV
If you design an SMPS, make it a standard practice to include a fuse and MOV. They ensure that your supply does not blow up in the field due to erratic input supply.

For the MOV, you may use 330V or higher rated part, since you mentioned your input supply in the range 180-280V. That should provide enough headroom. I design supplies for the range 180-265 and use 330V MOV. Works well for me.

For choosing the fuse, give this a read:
http://www.powerelectronics.com/passive-components/selecting-fuses-simple-procedures-get-right-overcurrent-protection-dc-dc-converte