Today (May 22, 2019), the carrier EE announced the launch of its 5G network in the UK, the first of its kind in this country. EE has also made some devices that are compatible with this network available. They include the OnePlus 7 Pro and the LG ThinQ V50.
https://www.notebookcheck.net/5G-network-launches-in-the-UK.421356.0.html
I've yet to see a successful 5G test run, LG failed in Seoul, China Mobile failed in Beijing, now EE claims to be commencing services in all those cities at once.