The way this works with British Telecom is that you have multiple SIDs on your router. There's one you connect to that you have control over, and there are also additional SIDs like "BTWifi-with-FON" and "BTWifi-X" with separate IP address and logging that you have no control over.
I think that BT internet customers have a free access to these all over the country and if they opt-out of this they can then get it disabled on their own home router. This way BT claims they literally have millions of WIFI access points all over the country, yet the experience is terrible if actually the network is on residential ADSL (upstream capped to 448kb/s for instance).
Incidentally I've wondered whether you could just replace their ADSL or VDSL (FTTC) router with something of your own without these additional access points and still been able to access their national network of access points for free.
Not quite the way it works bud. You DO have control over the public hotspot.. in settings you can turn it on or off.
Also it's a trivial matter to change router. I have this puppy which is future proof enough for me, can handle any isp/connection type(adsl,vdsl, cable) and when you run the Asuswrt-Merlin firmware . it gives you a lot more settings to tweat and explore and is a pretty fucking rock solid router and it looks sweet
BTW your BT connection username and password is user = BT passie = user i shit you not.
I left BT and moved to talktalk... I know. they are SHITE but at 26 quids all in for 80mb down and 20mb up including phone charges(just tell them you will go to sky.. they'll give you an offer) and i am 60 meters by wire from the cabinet. I am in the process of getting all the other flats on my stair to sign up to http://hyperoptic.com/
also.. i can STILL use my BT-wifi/FON login anywhere in the world and it's been 6 months since i left BT and i've used it here in Scotland, in England,in Portugal, Denver,Houston, Amsterdam New Jersey and the Republic of Ireland. it's the gift that keeps on giving as the turds are too lazy to check status more than the initial one