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That setting has disappeared. With wifi turned on, go to Settings > Wireless & networks > Wi-Fi settings > tap Forget in the BTWiFi and BTWiFi-with-FON SSIDs. You might have to do it again if you subsequently use BT Wi-Fi elsewhere, but it's OK for me.
It does seem to have gone.I have not noticed any problems, and there are a couple of nearby BT Wif hotspots, but my phone still connects to one of my home wifi signals.
this is how someone else solved the problem may or may not help you http://community.bt.com/t5/BB-Out-About/BT-WiFi-hotspot-taking-preference-over-my-home-hub/td-p/1082...
It always prioritised the weak and slow hotspot rather than the wifi I pay for even in my own house, when i was in other properties where the phone knows the password it would still insist on connecting to the weak hotspot . I found the app useless and deleted it