I think the new firmware has broken your Homehub, so I suggest you ask for a replacement.
If you find you can't trust BT you may consider lashing out up to £100 to purchase a 3rd party modem/router that BT can't break.
if you can stand the hassle I would phone again as you will get someone different and again ask for a replacement hub as this one is faulty the monitor 3/5 days and call back in majority of instances never happens and just a way to end the call