I had some sheets of plywood (12mm) delivered on 07/02/08. The following day I noticed some holes which looked like woodworm holes. I took a piece back to the store, where they were very helpful. They confirmed that it was woodworm, but reassured me that this, was quite common in plywood sold, and would be ok as the beetle would have died in the process, and therefore, would not spread.
However, I still feel a bit uneasy about using this wood.
I would rather spend a lot of extra time and effort in undoing the work I have done, than there be any possibility of an investation of woodworm. It would be helful to be advised on this matter.