Public trial planned for later this year.
Testing and trial is with EE. O2, Vodafone and Three are ongoing.
Will be available on 2G, 3G, 4G and also 5G.
The Flood Warning System is multi-channel, is possibles send warnings to go out via multiple channels.
In the UK a large number of phones are already enabled.
iPhone Cell Broadcast Message
Android Cell Broadcast Message
Demos in Lab: http://demo.fws.environment-agency.gov.uk/videos/