Hi,
As a hardware alternative, you can use a non BT modem/router with a BT service.
In difficult situations I recommend:
Billion BiPAC 7800DXL
Which you can get from the South American river place. At just under 100 notes it is not cheap, but in this case you get what you pay for.
It will do both ADSL and direct Ethernet connection to a fibre modem and as a backup you can plug in a 3g dongle.
In terms of wifi it has both 2.5Ghz and 5Ghz and you can run several virtual SSIDs to separate out users.
I have successfully used one in place of a BT HH5.
HTH
EG