Well and update I had reflashed my demo kindle and accidentally overwritten the area of the MMC that stores the S/N and MAC. I don't have the box any more so thought I was screwed!
While trolling the forums for ideas I found a thread where someone had a cracked screen and need to find out the serial number and someone suggested connecting it to the PC and reading the serial from device manager - which game me an epiphany!
I used USBDeview to lookup up the data of all USB devices installed on my computer and there it was! yay!
Using the MAC from another kindle the device is able to connect to Wifi but it is unable to register, or possibly it is unable to register due to the previous incorrect serial number being deregisted where this serial hasn't been resulting the kindle thinking it is deregisted when it isn't.
now I just need to figure out how to update the PCBA ID, and hopefully get the MAC from Amazon Support!