BT Business Hub 5 - Firmware Update

[#1]

So we've all established that BT Hubs will work on PlusNet, even BT admit this themselves.  I've got one that appears to have the firmware bug re intermittently disconnecting wireless sessions, BT admit a firmware update will cure this, but mine doesn't seem to want to update to the latest version.  Below is what my router says:
BT Business Hub 5 (Type A) | Software version 4.7.5.1.83.8.200 | Last updated 09/07/15
Any ideas how I can force a firmware update?

[#2]

You can't force an update, several people reported getting upgrades in the last couple of days, just leave it connected and it should get updated.