Righto, I fixed it.
Thanks for your quick replies though Kartu
I uninstalled Calibre, I was on an older .24 build.
removed all the files mentioned again, let the device rebuild.
Restarted my computer, and plugged the device back in then re-installed Calibre .37 build.
And Bingo. The correct combination.
Although I'm not sure why that worked, Calibre wasn't running while I wasn't trying to sync, or while I was rebuilding the xml.
I guess there MIGHT have been a library mismatch?, I read someone else got a corrupted dataabse that way in a search.
Anyway I'm fixed. Super happy.