Yes, the SP4 connected to a BT Fon connection somewhere. However, the Wifi settings said I was connecting to the home's private Wifi connection, for which my friend put in the password.
So, Wifi was showing available:
I selected Cheapside_WLAN and put in the password. This was shown as connected. I tried an internet page and got the BT_FON login page. I tried a couple of times including opening in a new tab and a Google search and a couple of times, Cheapside_WLAN was used. But then it stuck with BT_FON no matter what I tried, trying to download a file.
At this point I should be able to exclude a network, surely? But though there are things like 'forget network' for known details, I couldn't find 'never use this network' anyway.