E.E. Wi-Fi.Signal, Unlocked. Suddenly Appeared

Connected to it, opens up into a free EE service, at first it did not connect, eventually it finally connected.
Looks like they are testing a future paid for service..??
Marked as Wi-Fi 4

No, it's been around for years; it started with BT. It's the public EE WiFi network. It's broadcast from various nodes incl. New EE & BT BB routers unless you opt out of it via your MyEE a/c. So it could well come & go. New EE & BT BB users can connect to it for free @ https://ee-wifi.ee.co.uk/public/ee/index.htm using their EE & BT a/c creds if they have not opted out from it.

You are correct, it now shows a payable log on screen. Very much like the now abandoned V.M. Hotspot.