On my 8130 model pressing the TXT button on any of the channels except the HD ones brings up a screen that looks like the old CEEFAX screen with the page number in the top left. Not surprisingly, nothing happens.
Pressing the RED button at any other time brings up a SCAN menu.
However, flicking through the channels last week I did find the old Grand Prix highlights that I know run on the BBC red button service. The channel was marked something like "STREAM-1". So the video sections are there, you just have to hunt for them a bit.
In the book it says the TXT button is "Not available on this model". Which I assume to mean it doesn't actually work.
John