The bags, yes, the compost would need refreshing with a granular feed and have all the roots removed. However, with spuds you would risk building up diseases and the crop may not be as good next year. You should really replace the compost as a kind of 'crop rotation'.

As Volunteer says bags yes compost no, you can spread this around your flower bed though.

thanks moongrower/volunteer.i wasnt going to use the compost ,but i hate waste and wanted to use the bags if possible.

Don't throw the compost away, either spread around your flower beds or put in your compost bin.

dont worry moongrower im a dedicated recyclier, i re-use anything i can!thanks again for your advice

Have fun!