Thanks lbear but my Sony Bravia KDL-32EX724 TV does show the yellow panel at base of screen, and even allows me to navigate to other channels using it.
However, if I start on a BBC HD channel, press the red button and see the yellow panel, once I select a different BBC HD channel there's no sound. If I then use the yellow panel to go back to the original BBC HD channel the sound returns. No problem on BBC SD channels, so why is HD different?
I'm still hoping that the BBC can correct this, like they did a while back on another issue that effected loads of kit.