OllieB, I am sorry about your issue, however we can try to perform some troubleshooting. That way we will know if replacing the NUC would be necessary.
Since you have BIOS version 0023, we can try to reinstall the original BIOS v0018.You would need to do this using the BIOS recovery method. http://www.intel.com/support/motherboards/desktop/sb/CS-034524.htm
If this behavior persists please contact our Warranty Department so they can help you replacing your product http://www.intel.com/p/en_US/support/contactsupport
Please take into consideration that if the product was purchased less than 1 month ago, you would need to RMA your NUC through the place of purchase.
I recommend you updating the BIOS of the new NUC, but please install each BIOS version available.
EDIT: Some information posted here was not completely accurate as it was intended for older Intel® NUC models. For more information about the BIOS jumper please refer to pages 49-50 of the Technical Product Specification.
Many thanks for your response and the suggestions made. I did point out in my initial post that I already tried to perform a BIOS recovery but as the power button does not work I was unable to start the NUC.
The jumper setting 2-3 is new to me as I did not find this om my search of the Internet.
However last night I have managed to remove the motherboard from the case disconnect & connect the CMOS battery and put it all back together without breaking anything. After that exercise the power button worked again and I have since then upgraded to the new version of the BIOS.
Thanks for your help. I will post the 2-3 jumper solution on the xbmc forum as there are more users with this problem.