Solved! Go to Solution.
Its a known issue, and BT will be rolling out a fix once the testing is complete.
Meanwhile, you only need to restart the HH3, not the modem.
Using an alternative router will not stop your access to other BT Wifi hotspots, but you would not be transmitting BT Wifi.
BT now use a HH5 on its own, for Infinity, but there are other alternatives.