Unsure about iOS 12.1 having the UDID. From what I've read there are issues with the smart watch and iOS 12.1.
Apparently, you can install the beta profile and upgrade to iOS 12.1 without having your UDID or SEID registered. I just don't like that idea especially if it is not registered!
[doublepost=1537575663][/doublepost]I worked it out.
If you update to the latest version of Apple Configurator 2 from the Mac App Store, you can see it all in there.
The UDID format looks different to other model iOS devices.
XXXXXXXX-XXXXXXXXXXXXXXXX (no lower case characters anymore)