Try connecting to the BTWifi or BTWifi-With-Fon hotspot (BTOpenzone/BTFon).
Once your device is connected to the hotspot, open your browser.
If the BTWifi Login Landing page does not load, try going to https://www.btopenzone.com:8443/ while connected to the BTWifi hotspot.
Hope that works,
Have you tried "Forgetting" the network on your device?
Have you tried trying one restart of the Home Hub?
If you are trying to connect to some elses BTwifi hot spot they may have an issue with their hub or access to the internet.