OK thanks, good to know guys.
https://support.microsoft.com/en-us/help/4458469/windows-10-update-kb4458469
According to my winver I had/still have Version 1803 (build 17134.285), so I hadn't received/installed build 17134.319.
"Note This update has been re-released because of a missing solution. If you installed build 17134.319, please install this newer version of OS build 17134.320."
So I wasn't offered this update and still have Version 1803 (build 17134.285) after manually checking for updates, I got one and have done a reboot. I have just done another manual update check and I have 2018-09 Cumulative Update for Windows 10 Version 1803 for x64-based Systems (KB4458469) downloaded now.
Plus another one pending install:
2018-09 Update for Windows 10 Version 1803 for x64-based Systems (KB4100347).
Looks like I have some waiting for these to be installed. Just about to Restart again.
EDIT: OK looks like I now have everything - OS Build 17134.320.