I appear have found a way to force the BIS 8120 to use wi-fi in the browser, although this is not particularly practical or useful, but it might help those more technically minded than me to analyse what is happening.

In the browser I have gone to options and changed the default browser to wi-fi browser.

I have then gone to the manage connections menu and turned off mobile network by unchecking the box.

I have then turned off wi-fi in manage connections.

Conducting a scan of available networks then produces a prompt asking if I want to turn wi-fi on. If you reply yes to this, it shows me my saved home wi-fi network. Clicking on this gives a screen headed wi-fi security, with two fields, [b]Security type /B] and pre-shared key both of which are pre-filled, the first with pre-shared key and the second with the key itself. At the bottom of the page is a connect button. Clicking on this connects to the wi-fi network.

If I now open the browser, I have the heading wi-fi browser, and the wi-fi symbol that appears on the main screen now appears in the top right-hand corner. The browser then works on wi-fi. I have no idea why, and it is wholly impractical. Other data functions do not work - no email - in this setting. I hope this is helpful to someone.