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Hi Trixie,
Many thanks for your answer.
I have just been informed they are wood worm. The House Longhorn Beetle. The most destructive type.
We have just looked at packaging with skirting boards in delivered by Wickes and there they all are... millions of them.
We live in a very old house with 200 yr old beams.
We now have a major problem and exterminators will be called tomorrow.
I actually don't know how we go about proving Wickes delivered them though.... except we never had woodworm before, and have just had work done and the builders would have pointed them out I'm sure.
:(