Apple Watch with UK network provider
I go to university in America but use my UK sim and network for my iPhone. If I buy a Cellular Apple Watch in America, can I use my UK network for it in America?
There are 2 Apple Watch cellular radios
• Canada, U.S. Mexico, Puerto Rico
• The rest of the world
Carriers will not attempt to connect to an Apple Watch that does not use the correct radio.
If you do not get your Apple Watch in your own country, you may have to return the Apple Watch to the country where purchased to get warranty service.
If you do not get your Apple Watch in your own country, there may be country specific restrictions in the installed Apple Watch software that prevent features from working when you get home.
https://www.apple.com/watchos/feature-availability
As has been mentioned, there is no roaming, so even if your UK carrier will support the Apple Watch while you are in the UK, the Apple Watch will not use Roaming.
And even if it could use Roaming there is the 2 different radios and cellular networks. A UK Apple Watch will not talk to a U.S. cellular network.
You can use a UK Apple Watch in the U.S. as if it was a GPS ONLY Apple Watch, which will do everything a connected cellular model can do As Long As the iPhone is nearby.
